aptitude - boats & streams

7/24/2019 Aptitude - Boats & Streams

1/9

Aptitude :: Boats and Streams

Downstream/Upstream:

In water, the direction along the stream is called downstream. And, the direction againstthe stream is called upstream.

If the speed of a boat in still water is ukm/hr and the speed of the stream is v

km/hr, then:

Speed downstream = (u+ v) km/hr.

Speed upstream = (u- v) km/hr.

If the speed downstream is akm/hr and the speed upstream is bkm/hr, then:

Speed in still water =1

(a+ b) km/hr.

!ate o" stream

=

1(a- b) km/hr.

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,


2/9

find the time taken by the boat to go 6 km downstream.

A. ! ho"rs B. 3 ho"rs

C. 4 ho"rs D. # ho"rs

Answer & Explanation

Answer:$ption C

Explanation:

%peed downstream & '13 ( 4) km/hr & 1* km/hr.

+ime taken to travel 6 km downstream &6

hrs & 4 hrs.1*

!. A mans speed with the c"rrent is 1# km/hr and the speed of the c"rrent is !.# km/hr. +hemans speed against the c"rrent is-

A. .# km/hr B. km/hr

C. 1 km/hr D. 1!.# km/hr


Answer:$ption C

Explanation:

0ans rate in still water & '1# !.#) km/hr & 1!.# km/hr.

0ans rate against the c"rrent & '1!.# !.#) km/hr & 1 km/hr.

3. A boat r"nning "pstream takes ho"rs 4 min"tes to cover a certain distance, while it takes 4

ho"rs to cover the same distance r"nning downstream. 2hat is the ratio between the speed ofthe boat and speed of the water c"rrent respectively

A. ! - 1 B. 3 - !

C. - 3 D. annot be determined

E. 5one of these



3/9

Answer:$ption C

Explanation:

et the mans rate "pstream be xkmph and that downstream be ykmph.

+hen, distance covered "pstream in hrs 4 min & 7istance covered downstream in 4 hrs.

x8 4

& 'y8 4)#

44 x&4

y#

y&11

x.#

9e:"ired ratio &

y(

x -

y

x

! !

&

16

x 8 1 -

6

x 8 1

# ! # !

&

-3

# #

& - 3.

4. A motorboat, whose speed in 1# km/hr in still water goes 3 km downstream and comes back

in a total of 4 ho"rs 3 min"tes. +he speed of the stream 'in km/hr) is-

A. 4 B. #

C. 6 D. 1


Answer:$ption B

Explanation:

et the speed of the stream be xkm/hr. +hen,

%peed downstream & '1# ( x) km/hr,


4/9

%peed "pstream & '1# x) km/hr.

3(

3& 4

1

'1# ( x) '1# x) !

& !!# x! !

x!& !!#

x!& !#

x& # km/hr.

#. In one ho"r, a boat goes 11 km/hr along the stream and # km/hr against the stream. +he speed

of the boat in still water 'in km/hr) is-

A. 3 km/hr B. # km/hr

C. km/hr D. km/hr


Answer:$ption C

Explanation:

%peed in still water &

1

'11 ( #) kmph & kmph.

!


5/9

6. A boat r"nning downstream covers a distance of 16 km in ! ho"rs while for covering the same

distance "pstream, it takes 4 ho"rs. 2hat is the speed of the boat in still water

A. 4 km/hr B. 6 km/hr

C. km/hr D. 7ata inade:"ate


Answer:$ption B

Explanation:

9ate downstream &

16

kmph & kmph.!

9ate "pstream &16

kmph & 4 kmph.4

%peed in still water &1' ( 4) kmph & 6 kmph.

!

*. +he speed of a boat in still water in 1# km/hr and the rate of c"rrent is 3 km/hr. +he distance

travelled downstream in 1! min"tes is-

A. 1.! km B. 1. km

C. !.4 km D. 3.6 km


Answer:$ption D

Explanation:

%peed downstream & '1# ( 3) kmph & 1 kmph.

7istance travelled & 1 8

1!

km & 3.6 km.6

. A boat takes min"tes less to travel 36 miles downstream than to travel the same distance

"pstream. If the speed of the boat in still water is 1 mph, the speed of the stream is-

A. ! mph B. !.# mph

C. 3 mph D. 4 mph


6/9


Answer:$ption A

Explanation:

et the speed of the stream xmph. +hen,

%peed downstream & '1 ( x) mph,

%peed "pstream & '1 x) mph.

36

36&

'1 x) '1 ( x) 6

*!x8 6 & '1 x!)

x!( 4x( 1 &

'x( #)'x !) &

x& ! mph.

. A man can row at # kmph in still water. If the velocity of c"rrent is 1 kmph and it takes him 1ho"r to row to a place and come back, how far is the place

A. !.4 km B. !.# km

C. 3 km D. 3.6 km


Answer:$ption A

Explanation:

%peed downstream & '# ( 1) kmph & 6 kmph.

%peed "pstream & '# 1) kmph & 4 kmph.

et the re:"ired distance be xkm.


7/9

+hen, x

( x

& 16 4

!x( 3x& 1!

#x& 1!

x& !.4 km.

1.A boat covers a certain distance downstream in 1 ho"r, while it comes back in 1 ho"rs. If thespeed of the stream be 3 kmph, what is the speed of the boat in still water

A. 1! kmph B. 13 kmph

C. 14 kmph D. 1# kmph

E. 5one of these


Answer:$ption D

Explanation:

et the speed of the boat in still water be xkmph. +hen,

%peed downstream & 'x( 3) kmph,

%peed "pstream & 'x 3) kmph.

'x( 3) 8 1 & 'x 3) 83

!

!x( 6 & 3x

x& 1# kmph.


8/9

Data Sufficiency

Directions to Solve

;ach of the :"estions given below consists of a statement and / or a :"estion and two statements

n"mbered I and II given below it. oth I and II are necessary to answer


Answer:$ption E

Explanation:

I.%peed of the c"rrent & 1 km/hr.

II.?@ & 4 km.

et the speed of the boat in still water be xkm/hr. +hen,

4

(

4

& 3. +his gives x.'x(

1)

'x 1)

orrect answer is ';).

;ach of the :"estions given below consists of a :"estion followed by three statements.


9/9

to st"dy the :"estion and the statements and decide which of the statement's) is/are necessary to

answer the :"estion.

1. 2hat is the speed of the boat in still water

I. +he speed downstream is 1! kmph.

II. +he speed "pstream is 4 kmph.

III. In a to and fro o"rney between two points, the average speed of the boat was 6 kmph.

A. I and II only

B. All I, II and III

C. III, and either I or II

D. Any two of the three

E. 5one of these


Answer:$ption D

Explanation:

Brom I and II, speed of boat in still water &1

'1! ( 4) km/hr & km/hr.!

Brom II and III, we get-

Csing average speed &!xy

, we get-

! 8 4

8 y& 6

x(

y

4 ( y

y& !4 ( 6y

y& 1!.

9e:"ired speed &1

'1! ( 4) km/hr & km/hr.!

%imilarly, I and III also give the answer.

orrect answer is '7).

aptitude - boats & streams

Documents