topics for this presentation are 1. astronomical multiplication 2. cube root 3. square root,etc done...
TRANSCRIPT
Topics for this presentation are
1. Astronomical
multiplication
2. Cube root
3. Square root,etc
Done by
L.Hariharan
Aim:
To multiply
9999999993
*9999999994
Don’t try it in your calculator it will give you only an approximate value. Let us do it now mentally.
We will try to understand it with simple example
95 +5 { Nearest + or - to give 100,1000,etc}
* 92 +8
87 40 { 92-5 = 87 or 95-8 = 87 } and 8*5=40
Answer is 8740
Similarly answer for astronomical multiplication is
99999999870000000042
ANSWER
Now let us go to find cube roots
Background Last digit
13 = 1 1
23 = 8 8
33 = 27 7
43 = 64 4
53 = 125 5
63 = 216 6
73 = 343 3
83 = 512 2
93 = 729 9
Finding cube root requires some background
Examples :
9,261
1,728
32,768
175,616
Solution for 32,768
By seeing last digit we find last digit of cube root is equal to 2. (refer previous slide)
By seeing 32 we put 3, as our first digit as 33 = 27 is less than 32 and 43 = 64 is more.
Our answer is 32.
What is the square root of the number given below?
123456787654321
a) 1234569 b) 23456791 c) 11111111 d) 1267541
Note :
Expected time to solve the problem is 5 to 10 seconds
First of all the pattern:
Square of 1 = 1Square of 11 = 121Square of 111 = 12321Square of 1111 = 1234321Square of 11111 = 123454321Square of 111111 = 12345654321Square of 1111111 = 1234567654321And so on and so forth.
Answer choice is c
Note: No.s are arranged in knight movement as in the chess game. The sum is 260.
1 48 31 50 33 16 63 1830 51 46 3 62 19 14 3547 2 49 32 15 34 17 6452 29 4 45 20 61 36 135 44 25 56 9 40 21 60
28 53 8 41 24 57 12 3743 6 55 26 39 10 59 2254 27 42 7 58 23 38 11
