# Problems on Trains, Boats and Streams

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REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

Module Name: PROBLEMS ON TRAINS,BOATSAND STREAMS.SITAMS 1

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

MODULE OBJECTIVE: Decision making for planning, policy and management relies increasingly on the quantitative reasoning, which entails the collection, analysis and interpretation of quantitative data. This course is designed to introduce principles and techniques to solve trains, boats and streams related problems. Develop logical reasoning in a problem solving framework. One goal is to develop a disciplined logical analysis of word problems. Such reasoning is the foundation for buildings simple mathematical models of problems-models implicit on trains, boats and streams. However a logical mind will serve a person well in any field.

At the end of these course students: 1) To be able to understand the types of formulae used to calculate trains, boats and streams. 2) To be solving many problems related to trains, boats and streams which can be useful to students to face interviews

SITAMS

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PREREQUISITES: 1. a km/hr= (a* 5/18) m/s.

2. a m / s = (a*18/5) km/hr.

3 Time taken by a train of length 1 metres to pass a pole or a standing man or a signal post is equal to the time taken by the train to cover 1 metres.

4. Time taken by a train of length 1 metres to pass a stationary object of length b metres is the time taken by the train to cover (1 + b) metres.

5. Suppose two trains or two bodies are moving in the same direction at u m / s and v m/s, where u > v, then their relatives speed = (u - v) m / s.

6. Suppose two trains or two bodies are moving in opposite directions at u m / s and v m/s, then their relative speed is = (u + v) m/s.

7. If two trains of length a metres and b metres are moving in opposite directions at u m / s and v m/s, then time taken by the trains to cross each other = (a + b)/(u+v) sec.

8.If two trains of length a metres and b metres are moving in the same directionat u m / s and v m / s, then the time taken by the faster train to cross the slower train = (a+b)/(u-v) sec.

9. If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then (A's speet) : (Bs speed) = (b1/2: a1/2).

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SOLVED EXAMPLES: Ex.I. A train 100 m long is running at the speed of 30 km / hr. Find the time taken by it to pass a man standing near the railway line. (S.S.C. 2001) Sol. Speed of the train = (30 x 5/18_) m / sec = (25/3) m/ sec. Distance moved in passing the standing man = 100 m. Required time taken = 100/(25/3) = (100 *(3/25)) sec = 12 sec Ex. 2. A train is moving at a speed of 132 km/br. If the length of the train is110 metres, how long will it take to cross a railway platform 165 metres long? (Bank P.O.2004) Sol. Speed of train = 132 *(5/18) m/sec = 110/3 m/sec. Distance covered in passing the platform = (110 + 165) m = 275 m. Time taken =275 *(3/110) sec =15/2 sec = 7 sec Ex. 3. A man is standing on a railway bridge which is 180 m long. He finds that a train crosses the bridge in 20 seconds but himself in 8 seconds. Find the length of the train and its speed? (SASKEN 2003)

Sol. Let the length of the train be x metres, Then, the train covers x metres in 8 seconds and (x + 180) metres in 20 sec x/8=(x+180)/20 20x = 8 (x + 180) x = 120.

Length of the train = 120 m. Speed of the train = (120/8) m / sec = m / sec = (15 *18/5) kmph = 54 km Ex. 4. A train 150 m long is running with a speed of 68 kmph. In what time will it pass a man who is running at 8 kmph in the same direction in which the train is going? (WIPRO 2008) Sol: Speed of the train relative to man = (68 - 8) kmph = (60* 5/18) m/sec = (50/3)m/secSITAMS 4

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PROBLEMS ON TRAINS, BOATS AND STREAMS

Time taken by the train to cross the man

I

= Time taken by It to cover 150 m at 50/3 m / sec = 150 *3/ 50 sec = 9sec Ex. 5. A train 220 m long is running with a speed of 59 kmph. In what will it pass a man who is running at 7 kmph in the direction opposite to that in which the train is going? sol. Speed of the train relative to man = (59 + 7) kmph = 66 *5/18 m/sec = 55/3 m/sec. Time taken by the train to cross the man = Time taken by it to cover 220 m at (55/3) m / sec = (220 *3/55) sec = 12 sec Ex. 6. Two trains 137 metres and 163 metres in length are running towards each other on parallel lines, one at the rate of 42 kmph and another at 48 kmpb. In what time will they be clear of each other from the moment they meet? Sol. Relative speed of the trains = (42 + 48) kmph = 90 kmph =(90*5/18) m / sec = 25 m /sec. Time taken by the trains to'pass each other = Time taken to cover (137 + 163) m at 25 m /sec =(300/25) sec = 12 sec Ex. 7. Two trains 100 metres and 120 metres long are running in the same direction with speeds of 72 km/hr,In howmuch time will the first train cross the second? (TCS 2007)

Sol: Relative speed of the trains = (72 - 54) km/hr = 18 km/hr = (18 * 5/18) m/sec = 5 m/sec. Time taken by the trains to cross each other = Time taken to cover (100 + 120) m at 5 m /sec = (220/5) sec = 44 sec. Ex. 8. A train 100 metres long takes 6 seconds to cross a man walking at 5 kmph in the direction opposite to that of the train. Find the speed of the train.? Sol:Let the speed of the train be x kmph.SITAMS

Speed of the train relative to man = (x + 5) kmph = (x + 5) *5/18 m/sec.

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PROBLEMS ON TRAINS, BOATS AND STREAMS

Therefore 100/((x+5)*5/18)=6 30 (x + 5) = 1800 x = 55 Speed of the train is 55 kmph.

Ex. 9. A train running at 54 kmph takes 20 seconds to pass a platform. Next it takes.12 sec to pass a man walking at 6 kmph in the same direction in which the train is going . Find the length of the train and the length of the platform. (CAT 2006) Sol:Let the length of train be x metres and length of platform be y metres. Speed of the train relative to man = (54 - 6) kmph = 48 kmph = 48*(5/18) m/sec = 40/3 m/sec. In passing a man, the train covers its own length with relative speed. Length of train = (Relative speed * Time) = ( 40/3)*12 m = 160 m. Also, speed of the train = 54 *(5/18)m / sec = 15 m / sec. (x+y)/15 = 20 x + y = 300 Y = (300 - 160) m = 140 m. Ex10. A man sitting in a train which is traveling at 50 kmph observes that a goods train, traveling in opposite direction, takes 9 seconds to pass him. If the goods train is 280 m long, find its speed.?(ACCENTURE 2008) Sol: Relative speed = 280/9 m / sec = ((280/9)*(18/5)) kmph = 112 kmph. Speed of goods train = (112 - 50) kmph = 62 kmph. Ex. 11. Find the time taken by a train 180 m long, running at 72 kmph,in crossing an electric pole. Sol. Speed of the train = (72 x 5/18) m/sec = 20 m/sec. Distance moved in passing the pole = 180 m. Required time taken = (180/20) sec = 9 sec. Ex. 12. A train 140 m long is running at 60 kmph. In how much time wiU it pass a platform 260 m long? Sol. Speed of the train = (60 x 5/18) m/sec =50/3m/sec. Distance covered in passing the platform = (140 + 260) m = 400 m :. Time taken = (400 x 3/50) see = 24 sec.

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PROBLEMS ON TRAINS, BOATS AND STREAMS

Ex. 13. A man is standing on a railway bridge which is 180 m long. He finds that a train crosses the bridge in 20 seconds but himself in 8 seconds. Find the length of the train and its speed.(INFOSYS 2008) Sol. Let the length of the train be x metres. Then, the train covers x metres in 8 seconds and (x + 180) metres in 20 seconds. :. X/8 = (x + 180)/20 20x=8(x +180) x=120 :. Length of train = 120m. Speed of train = (120/8) m/sec = 15 m/sec = [15 X 18/5 ] Kmph = 54 Kmph. Ex. 14. A train 150 m long is running with a speed of 68 kmph. In what time will it pass a man who is running at 8 kmph in the same direction in which the train is going ? (BANK PO 2006) Sol. Speed of the train relative to man = (68 - 8) kmph = (60 x 5/18)m/see = 50/3 m/sec Time taken by the train to cross the man = Time taken by it to cover 150 m at ( 50/3)m/sec = (150 x 3/50 )sec = 9 sec. Ex. 15. A train 220 m long is running with a speed of 59 kmph. In what time will it pass a man who is running at 7 kmph in the direction opposite to that in which the train is going? (S.S.C 2004) Sol. Speed of the train relative to man = (59 + 7) kmph = (66 x 5/18 ) m/sec = ( 55/3) m/sec. Time taken by the train to cross the man :. (x + y)/15 = 20 or x + y = 300 or y =(300 160) m = 140m. :. Length of the platform = 140 m. Ex. 16. A man sitting in a train which is traveling at 50 kmph observes that a goods train, traveling in opposite direction, takes 9 seconds to pass him. If the goods train is 150 m long, find its speed.(HEXAWARE 2007) Sol. Relative speed = (150/9) m/sec =(150/ 9 x 18/5) kmph = 60 kmph. :. Speed of goods train = (60 - 50) kmph = 10 kmph.

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PROBLEMS ON TRAINS, BOATS AND STREAMS

EXERCISE PROBLEMS: 1. A train running at the speed of 60 km/hr crosses a pole in 9 seconds. What is the length of the train? (CSC 2008) A. 120 metres C. 324 metres Answer & Explanation Answer: Option D Explanation: 5 Speed= 60 x = 18 m/sec B. 180 metres D. 150 metres

50 3 m/sec. 50 x9 3 m = 150 m.

Length of the train = (Speed x Time) =

2. A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is: A. 45 km/hr C. 54 km/hr Answer & Explanation Answer: Option B Explanation: Speed of the train relative to man = = 125 10 m/sec B. 50 km/hr D. 55 km/hr

25 2 m/sec. 25 18 = x 2 5 km/hr = 45 km/hr. Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr. x - 5 = 45 x = 50 km/hr. 3. The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:(CTS 2009) A. 200 mSITAMS

B. 225 m8

REASONING AND QUANTITATIVE APTITUDE

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C. 245 m Answer & Explanation Answer: Option C Explanation: 5 25 Speed = 45 x = 18 m/sec 2 m/sec. Time = 30 sec. Let the length of bridge be x metres. 130 + x 25 Then, = 30 2 2(130 + x) = 750 x = 245 m.

D. 250 m

4. Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is.(IBM 2008) A. 1 : 3 C. 3 : 4 B. 3 : 2 D. None of these

Answer & Explanation Answer: Option B Explanation: Let the speeds of the two trains be x m/sec and y m/sec respectively. Then, length of the first train = 27x metres, and length of the second train = 17y metres. 27x + 17y = 23 x+ y 27x + 17y = 23x + 23y 4x = 6y x 3 = . y 2 5. A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform? A. 120 m C. 300 m Answer & Explanation Answer: Option B Explanation: 5 Speed = 54 x 18 m/sec = 15 m/sec. Length of the train = (15 x 20)m = 300 m.SITAMS 9

B. 240 m D. None of these

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

Let the length of the platform be x metres. x + 300 Then, = 15 36 x + 300 = 540 x = 240 m.

6. A train 240 m long passes a pole in 24 seconds. How long will it take to pass a platform 650 m long?(TCS 2006) A. 65 sec C. 100 sec Answer & Explanation Answer: Option B Explanation: 240 Speed = 24 m/sec = 10 m/sec. Required time = 240 + 650 sec = 89 sec. B. 89 sec D. 150 sec

7. Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is: A. 50 m C. 80 m Answer & Explanation Answer: Option A Explanation: Let the length of each train be x metres. Then, distance covered = 2x metres. Relative speed = (46 - 36) km/hr 5 = 10 x 18 m/sec 25 = 9 m/sec 2x 25 = 36 9 2x = 100 x = 50. 8. A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?(IGATE 2009)SITAMS 10

B. 72 m D. 82 m

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

A. 40 sec C. 45 sec Answer & Explanation Answer: Option A Explanation:

B. 42 sec D. 48 sec

Formula for converting from km/hr to m/s: X km/hr = 5 25 = m/sec. 18 m/sec 2 Total distance to be covered = (360 + 140) m = 500 m. Distance Formula for finding Time = Speed 500 x 2 Required time = = 40 sec. 25 sec Therefore, Speed = 45 x

Xx

5 m/s. 18

9. Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:(PATNI 2008) A. 36 C. 48 B. 45 D. 49

Answer & Explanation Answer: Option C Explanation: Relative speed = (60+ 90) km/hr 5 = 150 x 18 m/sec 125 = 3 m/sec. Distance covered = (1.10 + 0.9) km = 2 km = 2000 m. 3 Required time = 2000 x 125 sec = 48 sec. 10. A jogger running at 9 kmph alongside a railway track in 240 metres ahead of the engine of a 120 metres long train running at 45 kmph in the same direction. In how much time will the train pass the jogger? A. 3.6 sec C. 36 sec Answer & Explanation Answer: Option C Explanation:SITAMS 11

B. 18 sec D. 72 sec

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

Speed of train relative to jogger = (45 - 9) km/hr = 36 km/hr. 5 = 36 x 18 m/sec = 10 m/sec. Distance to be covered = (240 + 120) m = 360 m. 360 Time taken = = 36 sec. 10 sec

11. A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?(HCL 2009) A. 230 m C. 260 m E. None of these Answer & Explanation Answer: Option A Explanation: Relative speed = (120 + 80) km/hr 5 = 200 x 18 m/sec 500 = 9 m/sec. Let the length of the other train be x metres. x + 270 500 Then, = 9 9 x + 270 = 500 x = 230. 12. A goods train runs at the speed of 72 kmph and crosses a 250 m long platform in 26 seconds. What is the length of the goods train?(CTS 2005) A. 230 m C. 260 m Answer & Explanation Answer: Option D Explanation: 5 Speed = 72 x = 20 m/sec. 18 m/sec Time = 26 sec. Let the length of the train be x metres. Then, x + 250 = 20SITAMS 12

B. 240 m D. 320 m

B. 240 m D. 270 m

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

26 x + 250 = 520 x = 270. 13. Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is: (CAT 2010) A. 30 km/hr C. 60 km/hr Answer & Explanation Answer: Option C Explanation: Let the speed of the slower train be x m/sec. Then, speed of the faster train = 2x m/sec. Relative speed = (x + 2x) m/sec = 3x m/sec. (100 + 100) = 3x 8 24x = 200 25 x= . 3 50 So, speed of the faster train = m/sec 3 50 18 = x 3 5 km/hr = 60 km/hr. 14. Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is: A. 9 C. 10 Answer & Explanation Answer: Option D Explanation: 5 250 = 18 m/sec 9 m/sec. Distance covered in crossing each other = (140 + 160) m = 300 m. 9 54 Required time = 300 x = sec = 10.8 sec. 250 sec 5 Relative speed = (60 + 40) km/hr = 100 x 15. A train 110 metres long is running with a speed of 60 kmph. In what time will it13

B. 45 km/hr D. 75 km/hr

B. 9.6 D. 10.8

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REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

pass a man who is running at 6 kmph in the direction opposite to that in which the train is going? (INFOSYS 2006)

A. 5 sec C. 7 sec

B. 6 sec D. 10 sec

Answer & Explanation Answer: Option B Explanation: Speed of train relative to man = (60 + 6) km/hr = 66 km/hr. 5 = 66 x 18 m/sec 55 = 3 m/sec. 3 Time taken to pass the man = 110 x 55 sec = 6 sec. 16. A train travelling at a speed of 75 mph enters a tunnel 3 miles long. The train is mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges? A. 2.5 min C. 3.2 min Answer & Explanation Answer: Option B Explanation: Total distance covered = 7 1 + 2 4 15 miles. 4 miles B. 3 min D. 3.5 min

=

Time taken =

15 hrs 4 x 75 1 hrs 20 1 x 60 20 min.

=

=

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= 3 min. 17. A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is.(BANK PO 2009) A. 130 C. 500 Answer & Explanation Answer: Option C Explanation: 5 65 Speed = 78 x m/sec = m/sec. 18 3 Time = 1 minute = 60 seconds. Let the length of the tunnel be x metres. 800 + x 65 Then, = 60 3 3(800 + x) = 3900 x = 500. 18. A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform? A. 320 m C. 650 m Answer & Explanation Answer: Option B Explanation: 300 50 Speed = m/sec = m/sec. 18 3 Let the length of the platform be x metres. x + 300 50 Then, = 39 3 3(x + 300) = 1950 x = 350 m. 19. A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is: A. 50 m C. 200 m Answer & Explanation Answer: Option B Explanation:SITAMS 15

B. 360 D. 540

B. 350 m D. Data inadequate

B. 150 m D. Data inadequate

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PROBLEMS ON TRAINS, BOATS AND STREAMS

Let the length of the train be x metres and its speed by y m/sec. x x Then, = 15 y= . y 15 x + 100 x = 25 15 15(x + 100) = 25x 15x + 1500 = 25x 1500 = 10x x = 150 m.

20. A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?(S.B.I PO 2006) A. 69.5 km/hr C. 79 km/hr B. 70 km/hr D. 79.2 km/hr

Answer & Explanation Answer: Option D Explanation: Let the length of the train be x metres and its speed by y m/sec. x Then, = 8 x = 8y y x + 264 Now, =y 20 8y + 264 = 20y y = 22. 18 Speed = 22 m/sec = 22 x km/hr = 79.2 km/hr. 5 21. How many seconds will a 500 metre long train take to cross a man walking with a speed of 3 km/hr in the direction of the moving train if the speed of the train is 63 km/hr? A. 25 C. 40 B. 30 D. 45

Answer & Explanation Answer: Option B Explanation: Speed of the train relative to man = (63 - 3) km/hr = 60 km/hr = 60 x 5 18 m/sec

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=

50 3

m/sec. 3 50

Time taken to pass the man

=

500 x

sec

= 30 sec. 22. Two goods train each 500 m long, are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one.(CAT 2009) A. 12 sec C. 48 sec Answer & Explanation Answer: Option B Explanation: Relative speed = = (45 + 30) km/hr = 75 x 125 6 5 18 m/sec B. 24 sec D. 60 sec

=

m/sec.

We have to find the time taken by the slower train to pass the DRIVER of the faster train and not the complete train. So, distance covered = Length of the slower train. Therefore, Distance covered = 500 m. 6 Required time = 500 x = 24 sec. 125 23. Two trains are running in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then the speed of each train (in km/hr) is: A. 10 C. 36 B. 18 D. 72

Answer & Explanation Answer: Option C Explanation: Let the speed of each train be x m/sec. Then, relative speed of the two trains = 2x m/sec.SITAMS 17

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So, 2x =

(120 + 120) 12 2x = 20 x = 10. Speed of each train = 10 m/sec = 10 x

18 km/hr = 36 km/hr. 5 24. Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction? A. 10 C. 15 Answer & Explanation Answer: Option B Explanation: 120 m/sec = 12 m/sec. 10 120 Speed of the second train = m/sec = 8 m/sec. 15 Relative speed = (12 + 8) = 20 m/sec. (120 + 120) Required time = sec = 12 sec. 20 Speed of the first train = 25. A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is: A. 48 km/hr C. 66 km/hr Answer & Explanation Answer: Option D Explanation: Let the speed of the second train be x km/hr. Relative speed = (x + 50) km/hr = (x + 50) x 250 + 5x 18 5 18 m/sec B. 54 km/hr D. 82 km/hr B. 12 D. 20

=

m/sec.

Distance covered = (108 + 112) = 220 m. 220 =6 250 + 5xSITAMS 18

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18 250 + 5x = 660 x = 82 km/hr. 26. Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train? A. 23 m 7 27 m 9 B. 2 23 m 9

C.

D. 29 m

Answer & Explanation Answer: Option C Explanation: Relative speed = (40 - 20) km/hr = Length of faster train = 50 x5 9 20 x 5 50 m/sec = 18 9 250 7 m= m = 27 m. 9 9 m/sec.

27. A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:(S.S.C 2005) A. 45 m C. 54 m B. 50 m D. 72 m

Answer & Explanation Answer: Option B Explanation: 5 5 2 kmph = 2 x m/sec = m/sec. 18 9 5 10 4 kmph = 4 x m/sec = m/sec. 18 9 Let the length of the train be x metres and its speed by y m/sec. x x Then, 5 = 9 and 10 = 10. yy9 9 9y - 5 = x and 10(9y - 10) = 9x 9y - x = 5 and 90y - 9x = 100. On solving, we get: x = 50. Length of the train is 50 m. 28. A train overtakes two persons walking along a railway track. The first one walks at 4.5 km/hr. The other one walks at 5.4 km/hr. The train needs 8.4 and 8.5 secondsSITAMS 19

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respectively to overtake them. What is the speed of the train if both the persons are walking in the same direction as the train? A. 66 km/hr C. 78 km/hr B. 72 km/hr D. 81 km/hr

Answer & Explanation Answer: Option D Explanation: 5 5 4.5 km/hr = 4.5 x m/sec = m/sec = 1.25 m/sec, and 18 4 5 3 5.4 km/hr = 5.4 x m/sec = m/sec = 1.5 m/sec. 18 2 Let the speed of the train be x m/sec. Then, (x - 1.25) x 8.4 = (x - 1.5) x 8.5 8.4x - 10.5 = 8.5x - 12.75 0.1x = 2.25 x = 22.5 18 Speed of the train = 22.5 x km/hr = 81 km/hr. 5 29. A train travelling at 48 kmph completely crosses another train having half its length and travelling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is A. 400 m C. 560 m B. 450 m D. 600 m

Answer & Explanation Answer: Option A Explanation: Let the length of the first train be x metres. x Then, the length of the second train is metres. 2 5 Relative speed = (48 + 42) kmph = 90 x m/sec = 25 m/sec. 18 [x + (x/2)] 3x = 12 or = 300 or x = 200. 25 2 Length of first train = 200 m. Let the length of platform be y metres. 5 40 Speed of the first train = 48 x m/sec = m/sec. 18 3 3 (200 + y) x = 45 40 600 + 3y = 1800SITAMS 20

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PROBLEMS ON TRAINS, BOATS AND STREAMS

y = 400 m 30. Two stations A and B are 110 km apart on a staright line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet? (ACCENTURE 2007) A. 9 a.m. C. 10.30 a.m. B. 10 a.m. D. 11 a.m.

Answer & Explanation Answer: Option B Explanation: Suppose they meet x hours after 7 a.m. Distance covered by A in x hours = 20x km. Distance covered by B in (x - 1) hours = 25(x - 1) km. 20x + 25(x - 1) = 110 45x = 135 x = 3. So, they meet at 10 a.m. 31. Two, trains, one from Howrah to Patna and the other from Patna to Howrah, start simultaneously. After they meet, the trains reach their destinations after 9 hours and 16 hours respectively. The ratio of their speeds is:(IBM 2006) A. 2 : 3 C. 6 : 7 Answer & Explanation Answer: Option B Explanation: Let us name the trains as A and B. Then, (A's speed) : (B's speed) = b : a = 16 : 9 = 4 : 3. B. 4 : 3 D. 9 : 16

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QUESTION BANK: 1. A train moves with a speed of t 08 kmph. Its speed in meters per second is : (a) 38.8 (b) 18 (c) 30 2. A speed of 14 meters per second is the same as : (a) 50.4 km/Hr (b) 28 km/hr (c) 70 km/hr (d) 46.6 km/hr

3. A man on riding crosses a bridge in 5 minutes when riding is being done at 15 kmph. The. length of the bridge is : (a) 125 m (b) 250 m (c) 1250 m (d) 2500 m

4. A train 150 m long is running at a speed of 90 kmph. Time taken by the train to cross a tree is : (a) 3 see (b) 4 see (c) 6 see (d) 8 see

5. A train 280 m long, running with a speed of 63 kmIhr will pass an electric pole in : . (a) 20 see (b) 16 see (c) 15 sec (d) 18 sec 6. A train is moving at a speed of 132 kmph. If the length of the train is 110 meters, how long will it take to cross a railway platform 165 m . long? (a) 5 see (b) 7.5 see (c) 10 see (d) 15 sec

7. A train 280 m long is moving at 60 kmph. The time taken by the train to cross a tunnel 220 m long, is : (a) 20 sec (b). 25sec (c) 30 sec (d) 35 sec

8.With a speed of 60 kmph a train crosses a pole in 30 seconds. The length of the train is : (a) 1000 m (b) 900 m (c) 750 m (d) 500 m

9. A train traveling at a speed of 90 kmph, crosses a pole in 10 seconds. The length of the train is: a) 250 m (b) 150 m. (c) 900 m (d) 100 m 10. A train 120 m long crosses a standing man in 15 seconds. The speed of the train is : (a) 32 km/hr (b) 36.5 km/hr (c) 28.8 km/hr (d) 40 km/hr

11. A train 700 m long is running at 72 kmph. If it crosses a tunnel in 1 minute, the length of the tunnel is :SITAMS 22

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

(a) 700 m

(b) 600 m

(c) 550 m

(d) 500 m

12. The length of a bridge which a train 130 m long and traveling at 45 kmph can cross in 30 seconds, is : (a) 200 m (b) 225 m (c) 245 m (d) 250 m

13. If a 200 m long train crosses a platform of the same length as that of the train in 20 seconds, then the speed of the train is: (a) 50 km/hr (b) 60 km/hr (c) 72 km/hr (d) 80 km/hr

14. A train 60 m long passes a platform 90 m long in 10 seconds. The speed of the train is : (a)'10 km/hr (b) 15 km/hr (c) 54 km/hr (d) 48 km/hr

15. A train 300 m long crossed a platform 900 m long in 1 minute 12 seconds. The speed of the train (in km/hr) is : (a) 45 (b) 50 (c) 54 (d) 60 16. A train crosses a platform 100 m long in 60 seconds at a speed of 45 kmph. The time taken by the train to cross an electric pole is : (a) 8 sec (b) 52 sec (c) 1 minute (d) data inadequate

17. A train of length 150 m takes 40.5 seconds to cross a tunnel of length 300 m. The speed of the train (in km/hr) is : (a) 13.33 (b) 26.67 (c) 40 (d) 400

18. A .train 150 m long takes 20 seconds to cross a platform 450 m long. The speed of the train (in m/sec) is : (a) 22.5 (b) 30 (c) 45 (d) 96

19. A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is : (a) 200 m (b) 150 m (c) 50 m (d) data inadequate

20. A train takes 18 seconds to pass completely through a station 162 m long and 15 seconds through another station 120 m long. The length of the train is : (a) 70 mSITAMS

(b) 80 m

(c) 90 m

(d) 100 m23

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

21. If a train 110 m long passes a telegraph pole in 3 seconds, then the time taken by it to cross a railway platform 165 m long, is (a) 3 sec (b) 4 sec (c) 5 sec (d) 7.5 sec

22. A train 110 m long is traveling at a speed of 58 kmph. The time in which it will pass a passer by, walking at 4 kmph in the same direction,is : (a) 6 sec (b) 7 sec (c) 7 1/3 see (d) 7 1/3 min

23. A train 150 m long moving at a speed of 25 meters per second overtakes a man moving at 5 meters/see in opposite direction. The train will pass, the man in : (a) 5 sec (b) 6 see (c) 4 2/7 sec (d) 8 see

24. Two trains 200 m and 150 m long are running on parallel rails at the rate of 40 kmph and 45 kmph respectively. In how much time will they cross each other, if they are running in the same direction? (a) 72 sec (b) 132 sec (c) 192 sec (d) 252 see

25. Two trains 126 m and 114 m long are running in opposite directions, one at the rate of 30 kmph and another one at 42 kmph. From the moment they meet will cross each other in : (a) 10 sec (b) 11 sec (c) 12 sec (d) 13 sec

26. A train 270 m long is moving at a speed of 24 kmph. It will cross a man coming from the opposite direction at a speed of 3 kmph, in : (a) 24 sec (b) 28 sec (c) 32 see (d) 36 sec

27. A train 125 m long passes a man, running at 5 kmph in the same direction in which the train is going, in 10 seconds. The speed of the train is : (a) 50 km/hr (b) 45 km/hr (c) 55 km/hr (d) 54 km/hr

28. A train 11 0 m long passes a man, running at 6 kmph in the direction opposite to that of the train, in 6 seconds. The speed of the train is : (a) 60 km/hr (b) 66 km/hr (c) 54 km/hr (d) 72 km/hr

29. Two trains are moving in the same direction at 65 kmph and 45 kmph. The faster train crosses a man in slower train in 18 seconds. The length of the faster train is: . (a) 120 mSITAMS

(b) 180 rn

(c) 100 m

(d) 145 m24

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

30. A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is : (a) 48 kmph (b) 54kmph (c) 66 kmph (d) 82 kmph

31. A train B speeding with 120 kmph crosses another train C, running in the same direction in 2 minutes. If the lengths of the trains B and C be 100 m and 200 m respectively, what is the speed of the train C? (a). 111 kmph (b) 127 kmph (c) 123 kmph (d) 129 kmph 32. Two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the fasten train in 8 seconds. The length of the faster train is : (a) 80 m (b) 100 m (c) 120 m (d) 180 m

33. The length of a running train A is 30% more than the length of another train B running in the opposite direction. To find out the speed of the train B, which of the following information given in statements P and Q is sufficient? P : The speed of train A is 80 kmph. Q : They took 90 seconds to cross each other. (a) Either P or Q is sufficient (b) Both P and Q are not sufficient (c) Only Q is sufficient (d) Both P and Q are needed 34. The speed of a 100 m long running train A is 40% more than the speed of another 180 m long train B running in the opposite directions. To find out the speed of train B, which of the information given in statements P and Q is sufficient? P : The two trains crossed each other in 6 seconds. Q : The difference between the speeds of the two trains was 26 kmph. (a) Only P is sufficient (b) Only Q is sufficient (c) Both P and Q are needed (d) Both P & Q are not sufficient 35. A train running at certain speed crosses a stationary engine in 20 seconds. To find out the speed of the train, which of the following information is necessary: (a) Only the length of the train (b) Only the length of the engine (c) Either the length of the train or the length of the engine (.d) Both the length of the train and the length of the engine 36.' A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is :

SITAMS

25

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

(a) 72 m

(b) 54 m

(c) 50 m

(d) 45 m

37. Two stations A and B are 110 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet? (a) 9 a.m. (b) 10 a.m. (c) 11 a.m. (d) 10.30 a.m.

38. A train X starts from Meerut at 4 P.M. and reaches Ghaziabad at 5 P.M. while another train Y starts from Ghaziabad at 4 P.M. and reaches Meerut, at 5.30 PM. The two trains will cross each other at : (a) 4.36 p.m. (b) 4.42 p.m. (c) 4.48 p.m. (d) 4.50 p.m.

39. Two trains running in the same direction at 65 kmph and 47 kmph, completely pass one another in 1 minute. If the length of the first train is 125 m, the length of the second train is : (a) 125 m " (b) 150 m' (c) 175 m (d) 200 m

40. Two' trains are running in opposite directions towards each other with speeds of 54 kmph and 48 kmph respectively. If the length of one train is 250 m and they cross each other in 18 seconds, the length of the other train is : (a) 145 m (b) 230 m (c) 260 m (d) 180 m

41. A train 150 m long passes a km stone in 15 seconds and another train of the same length travelling in opposite direction in 8 seconds. The speed of the second train is : (a) 60 kmph (b) 72 kmph (c) 66 kmph (d) 99 kmph

42. A train traveling at 48 kmph completely crosses another train having half its length and traveling in opposite direction at 42 kmph, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is : (a) 560 m (b) 400 m (c) 600 m (d) 450 m

43. A train is running at the rate of 60 kmph. A man is also going in the same direction on a track parallel to the rails at a speed of 45 kmph. If the train crosses the man in 48 seconds, the length of the train is : (a) 50 m (b) 100 m (c) 150 m (d) 200 m

44 A train of length 150 m takes 10 seconds to pass over another train 100 m long coming from the opposite direction. If the speed of the first train be 30 kmph, the speed of the second train is :

SITAMS

26

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

(a) 36 kmph

(b) 54 kmph

(c) 60 kmph (d) 72 kmph

45. A man sees a train passing over a bridge 1 km long. The length of the train is half that of the bridge. If the train clears the bridge in 2 minutes, the speed of the train is : (a) 30 km/hr (b) 45 km/hr (c) 50 km/hr (d) 60 km/hr

ANSWERS 1. (c) 2. (a) 3. (c)

4. (c) 5. (b)

6. (b) 7. (c) 8. (d)

9. (a) 10. (c)

11. (d) 12. (c) 13. (c) 14. (c) 15. (d) 16. (b) 17. (c) 18. (b) 19. (b) 20. (c) 21. (d) 22 (c) 23. (a) 24. (d) 25. (c) 26. (d) 27. (a) 28. (a) 29. (c) 30. (d) 31. (a) 32. (d) 33. (b) 34. (a) 35. (d) 36. (c) 37. (b) 38. (a) 39. (c) 40. (c) 41. (d) 42. (b) 43. (d) 44. (c) 45. (b)

SITAMS

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PROBLEMS ON TRAINS, BOATS AND STREAMS

PROBLEMS ON BOATS AND STREAMSPREREQUISITES: 1.In water ,the direction along the stream is called downstream and ,the direction against the stream is called upstream. 2.If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr,then: speed downstream=(u+v)km/hr. speed upstream=(u-v)km/hr. 3.If the speed downstream is a km/hr and the speed upstream is b km/hr,then : speed in still water=1/2(a+b)km/hr rate of stream=1/2(a-b)km/hr SOLVED EXAMPLES: EX.1.A man can row upstream at 7 kmph and downstream at 10kmph.find mans rate in still water and the rate of current. Sol. Rate in still water=1/2(10+7)km/hr=8.5 km/hr. Rate of current=1/2(10-7)km/hr=1.5 km/hr. EX.2. A man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2hours30minutes to cover a distance of 5km upstream. find the speed of the river current in km/hr. Sol. rate downstream=(15/3 )km/hr=(15*4/15)km/hr=4km/hr. Rate upstream=(5/2 )km/hr=(5*2/5)km/hr=2km/hr. Speed of current=1/2(4-2)km/hr=1km/hr EX.3. a man can row 18 kmph in still water.it takes him thrice as long to row up as to row down the river.find the rate of stream. Sol. Let mans rate upstream be x kmph.then ,his rate downstream=3xkmph. So,2x=18 or x=9. Rate upstream=9 km/hr,rate downstream=27 km/hr. Hence,rate of stream=1/2(27-9)km/hr=9 km/hr.SITAMS 28

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

EX.4. there is a road beside a river.two friends started from a place A,moved to a temple situated at another place B and then returned to A again.one of them moves on a cycle at a speed of 12 km/hr,while the other sails on a boat at a speed of 10 km/hr.if the river flows at the speed of 4 km/hr,which of the two friends will return to placeA first? Sol. Clearly the cyclist moves both ways at a speed of 12 km/hr. The boat sailor moves downstream @ (10+4)i.e.,14 km/hr and upstream @ (10-4)i.e., 6km/hr. So,average speed of the boat sailor=(2*14*6/14+6)km/hr =42/5 km/hr=8.4 km/hr. since the average speed of the cyclist is greater ,he will return ta A first. EX.5. A man can row 7 kmph in still water.if in a river running at 1.5 km/hr an hour,it takes him 50 minutes to row to a place and back,how far off is the place? Sol. Speed downstream =(7.5+1.5)km/hr=9 km/hr; Speed upstream=(7.5-1.5)kmph=6kmph. Let the required distance be x km.then, x/9+x/6=50/60. 2x+3x=(5/6*18) 5x=15 x=3. Hence,the required distance is 3km. EX.6. In a stream running at 2kmph,a motar boat goes 6km upstream and back again to the starting point in 33 minutes.find the speed of the motarboat in still water. Sol.let the speed of the motarboat in still water be x kmph.then, 6/x+2 +6/x-2=33/60 11x2-240x-44=0 11x2-242x+2x-44=0 (x-22)(11x+2)=0 x=22.SITAMS 29

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

EX.7.A man can row 40km upstream and 55km downstream in 13 hours also, he can row 30km upstream and 44km downstream in 10 hours.find the speed of the man in still water and the speed of the current. Sol.let rate upstream=x km/hr and rate downstream=y km/hr. Then,40/x +55/y =13(i) and 30/x +44/y =10 Multiplying (ii) by 4 and (i) by 3 and subtracting ,we get:11/y=1 or y=11. Substituting y=11 in (i),we get:x=5. Rate in still water =1/2(11+5)kmph=8kmph. Rate of current=1/2(11-5)kmph=3kmph

SITAMS

30

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

EXERCISE PROBLEMS: 1. A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream. (WIPRO 2007) A. C. 2 hours 4 hours B. D. 3 hours 5 hours

Answer & Explanation Answer: Option C Explanation: Speed downstream = (13 + 4) km/hr = 17 km/hr. Time taken to travel 68 km downstream = 68 17 hrs = 4 hrs.

2. A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is: (IGATE 2009) A. C. 8.5 km/hr 10 km/hr B. D. 9 km/hr 12.5 km/hr

Answer & Explanation Answer: Option C Explanation: Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr. Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr. 3. A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?(TCS 2004) A. C. E.SITAMS

2:1 8:3 None of these

B. D.

3:2 Cannot be determined

31

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

Answer & Explanation Answer: Option C Explanation: Let the man's rate upstream be x kmph and that downstream be y kmph. Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs. xx8 4 5 = (y x 4)

44 x =4y 5 11 y = x. 5 Required ratio = 16x 1 x 5 2 8 3 = : 5 5 = =8:3 4. A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is: A. C. 4 6 B. D. 5 10 : y+x 2 6x 1 x 5 2 : y-x 2

Answer: Option B Explanation: Let the speed of the stream be x km/hr. Then, Speed downstream = (15 + x) km/hr, Speed upstream = (15 - x) km/hr. 30 30 1 + =4 (15 + x) (15 - x) 2SITAMS 32

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

900 9 2 = 225 - x 2 9x2 = 225 x2 = 25 x = 5 km/hr. 5. In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is.(HCL 2008) A. C. 3 km/hr 8 km/hr B. D. 5 km/hr 9 km/hr

Answer & Explanation Answer: Option C Explanation: 1 Speed in still water = (11 + 5) kmph = 8 kmph. 2 6. A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water? A. C. 4 km/hr 8 km/hr B. D. 6 km/hr Data inadequate

Answer & Explanation Answer: Option B Explanation: Rate downstream = Rate upstream = 16 2 kmph = 8 kmph.

16 4 kmph = 4 kmph. 1 Speed in still water = (8 + 4) kmph = 6 kmph. 2

SITAMS

33

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

7. The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is: A. C. 1.2 km 2.4 km B. D. 1.8 km 3.6 km

Answer & Explanation Answer: Option D Explanation: Speed downstream = (15 + 3) kmph = 18 kmph. Distance travelled = 18 x 12 60 km = 3.6 km.

8. A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is:(ACCENTURE 2007) A. C. 2 mph 3 mph B. D. 2.5 mph 4 mph

Answer & Explanation Answer: Option A Explanation: Let the speed of the stream x mph. Then, Speed downstream = (10 + x) mph, Speed upstream = (10 - x) mph. 36 36 90 = (10 - x) (10 + x) 60 72x x 60 = 90 (100 - x2) x2 + 48x - 100 = 0

SITAMS

34

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

(x+ 50)(x - 2) = 0 x = 2 mph.

9. A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place? A. C. 2.4 km 3 km B. D. 2.5 km 3.6 km

Answer & Explanation Answer: Option A Explanation: Speed downstream = (5 + 1) kmph = 6 kmph. Speed upstream = (5 - 1) kmph = 4 kmph. Let the required distance be x km. Then, x x + =1 6 4

2x + 3x = 12 5x = 12 x = 2.4 km. 10. A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water? A. C. E. 12 kmph 14 kmph None of these B. D. 13 kmph 15 kmph

Answer & Explanation Answer: Option DSITAMS 35

REASONING AND QUANTITATIVE APTITUDE

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Explanation: Let the speed of the boat in still water be x kmph. Then, Speed downstream = (x + 3) kmph, Speed upstream = (x - 3) kmph. (x + 3) x 1 = (x - 3) x 2x + 6 = 3x - 9 x = 15 kmph. 11. A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water? (CSC 2008) A. C. 40 minutes 1 hr 15 min B. D. 1 hour 1 hr 30 min 3 2

Answer & Explanation Answer: Option C Explanation: Rate downstream = 1 x 60 10

km/hr = 6 km/hr.

Rate upstream = 2 km/hr. 1 Speed in still water = (6 + 2) km/hr = 4 km/hr. 2 5 1 Required time = hrs = 1 hr 15 min. 4 hrs = 14 12. A man can row three-quarters of a kilometre against the stream in 11 down the stream in 7 minutes and

minutes. The speed (in km/hr) of the man in still water is: (SBI P.O 2001)

A.SITAMS

2

B.

336

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

C.

4

D.

5

Answer: Option D Explanation: We can write three-quarters of a kilometre as 750 metres, and 11 minutes as 675 seconds. 750 10 = m/sec. 675 m/sec 9 750 5 Rate downstream = = m/sec. 450 m/sec 3 1 10 5 Rate in still water = + 2 9 3 m/sec 25 = m/sec 18 25 18 = x 18 5 km/hr Rate upstream = = 5 km/hr. 13. Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is.(S.S.C 2005) A. C. 16 hours 20 hours B. D. 18 hours 24 hours

Answer & Explanation Answer: Option D Explanation: Speed upstream = 7.5 kmph. Speed downstream = 10.5 kmph. Total time taken =SITAMS

105 105 + 7.5 10.5 hours = 24 hours.37

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

14. A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is: A. C. 2:1 3:2 B. D. 3:1 4:3

Answer & Explanation Answer: Option B Explanation: Let man's rate upstream be x kmph. Then, his rate downstream = 2x kmph. (Speed in still water) : (Speed of stream) = = 3x x : 2 2 2x + x 2 : 2x - x 2

= 3 : 1. 15. A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is.(BANK PO 2008) A. C. 1 km/hr 2 km/hr B. D. 1.5 km/hr 2.5 km/hr

Answer: Option A Explanation: Suppose he move 4 km downstream in x hours. Then, Speed downstream = Speed upstream =SITAMS

4 x

km/hr.

3 x

km/hr.38

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

48 48 1 + = 14 or x = . (4/x) (3/x) 2 So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr. 1 Rate of the stream = (8 - 6) km/hr = 1 km/hr. 2

SITAMS

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QUESTION BANK: 1. If a man can swim downstream at 6 kmph and upstream at 2 kmph, his speed in still water'is : (a) 4 km/hr (b) 2 km/hr (c) 3 km/hr (d) 2.5 km/hr 2. A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is : (a) 5 km/hr (b) 2.5 km/hr (c) 10.5 km/hr (d) 4.2 km/hr 3. If Anshul rows 15 km upstream and 21 km downstream taking 3 hours each time, then the speed of the stream is : (a) 1 km/hr (b) 1.5 km/hr (c) 2 km/hr (d) 12 km/hr 4. A man rows 750 m in 675 seconds against the stream and returns in 7 minutes. His rowing speed in still water is: (a) 3 km/hr (b) 4 km/hr (c) 5 km/hr (d) 6 km/hr 5. A man rows 13 km upstream in 5 hours and also 28 km downstream in 5 hours. The velocity of the stream is : (a) 1.5 km/hr (b) 2 km/hr ( c) 2.5 km/hr (d) 3 km/hr 6. If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 3 kmph, then the speed of the boat in still water is: (a) 4.2 km/hr (b) 9 km/hr (c) 13 km/hr (d) 21 km/hr 7. A man can row 9 1/3 kmph in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. The speed of the current is : (a) 3 1/3 km/hr (b) 3 1/9 km/hr (c) 4 2/3 km/hr (d) 14 km/hr 8. A man can row a boat at 10 kmph in still water. If the speed of the stream is 6 kmph, the time taken to row a distance of 80 km down the stream is : (a) 8 hours (b) 5 hours (c) 10 hours (d) 20 hours 9. A boat takes 4 hours for travelling downstream from point A to point B and coming back to point A upstream. If the velocity of the stream is 2 kmph and the speed of the boat in still water is 4 kmph, what is the distance between A and B ? (a) 4 kms (b) 6 km (c) 8 km (d) 9 km 10. If a man rows at 6 kmph in still water and 4.5 kmph against the current, then his rate along the current is (a) 9.5 km/hr (b) 7.5 km/hr (c) 7 km/hr (d) 5.25 km/hr 11. If a man's rate with the current is 11 kmph and the rate of the current is 1.5 kmph, then the man's rate against the current is :SITAMS 40

REASONING AND QUANTITATIVE APTITUDE

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(a) 8 km/hr

(b) 9.5 km/hr (c) 9 km/hr

(d) 6.25 km/hr

12. Speed of a hoat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. man rows to a place at a distance of 10.5 km and comes back to the starting point. The total time taken by him is : (a) 16 hours (b) 18 hours (c) 20 hours (d) 24 hours 13. A boat moves upstream at the rate of 1 km in 10 minutes and downstream at the rate of 1 km in 6 minutes. The speed of the current is : (a) 1 km/hr (b) 1.5 km/hr (c) 2 km/hr (d) 2.5 km/hr 14. River is running at 2 kmph. If takes a man twice as long to row up as to row down the river. The rate of the man in still water is : (a) 6 km/hr (b) 4 km/hr (c) 10 km/hr (d) 8 km/hr 15. A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is : (a) 1 km/hr (b) 1.8 km/hr (c) 3.5 km/hr (d) 1.5 km/hr 16. The current of stream runs at 1 kmph. A motor boat goes 35 km upstream and back again to the starting point in 12 hours. The speed of the motor boat in still water is : (a) 6 km/hr (b) 7 km/hr (c) 8 km/hr (d) 8.5 km/hr 17. A boat covers 24 km upstream and 36 km downstream in 6 hours while it covers 36 km upstream and 24 km downstream in 6 hours. The velocity of the current is : (a) 1 km/hr (b) 1.5 km/hr (c) 2 km/hr (d) 2.5 km/hr 18. A man can row three-quarters of a kilometer against the stream in 11 minutes and returns in 7 minutes. The speed of the man is still water is : (a) 2 km/hr (b) 3 km/hr (c) 4 km/hr (d) 5 km/hr 19. The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is : (a) 3.6 km (b) 2.4 km (c) 1.2 km (d) 1.8 km 20. A man can row 5 kmph in still water. If the river is running at 1kmph, it takes him 75 minutes to row to a place and back. How far is the place? (a) 3 km (b) 2.5 km (c) 4.km (d) 5 km . 21. If a man rows at the rate of 5 kmph in still water and his rate against the current is 3.5 kmph, then the man's rate along the current is : (a) 4.25 kmph (b) 6 kmph (c) 6.5 kmph (d) 8.5 kmph ANSWERSSITAMS 41

REASONING AND QUANTITATIVE APTITUDE

PROBLEMS ON TRAINS, BOATS AND STREAMS

1.(a) 2.(b) 3.(a) 4.(c) 5.(a) 6.(c) 7.(c) 8.(b) 9.(b) 10.(b) 11.(a) 12.(a) 13.(c) 14.(a) 15.(a) 16.(a) 17.(c) 18.(d) 19.(a) 20.(a) 21.(c)

SITAMS

42

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