Quants

Question 1

Sum of square of n natural numbers

Answer 1

n(n+1)(2n+1)/6

Question 2

Squares of numbers with 5 at end

Answer 2

25 at last and first number * first number +1
25^2 = (2*3)= 6 ->625

Question 3

Percantages with numbers like 30 %, 5%

Answer 3

Calculate 10% and multiply or divide n
By another number to arrive at.. example for 30% calculate for 10% and multiply by 3 and for 5% divide by 2.

Question 4

Dividing by 5 shortcut

Answer 4

Mutiply by 2 and then divide by 10
Example 630/5
630*2 = 1260
1260/10 = 126

Question 5

Mutiply two numbers shortcut using doubling and halving

Answer 5

Divide on one side and multiply in other side
Ex 1635
16/2 * 352
870
560
Simply using factorization
16 becomes 82
8235 = 8*70 = 560

Question 6

Multiply using factorization used when

Answer 6

One number ends in 5 or 50
The other number is even

Question 7

Multiply using 25 75 ends

Answer 7

Using factorization convert the 25 or 75 into 100 or 50 and then multiply
Ex 5625 = 28225 = 2850 = 142500 = 14*100= 1400

Question 8

Squaring by knowing previous square

Answer 8

Eg. 7^2 = 49. So 8^2 will be 49+7+8=64

Which is n^2 is known then
(n+1)^2 = n^2+n+n+1

Question 9

Backsolving

Answer 9

When all answers are numbers (the numbers will be in increasing order), use this method and select option as C and back solve the problem and check