# Mathematics Tricks – Part 3

This is the continuation of my previous post

## Multiply any two digit number by 11

Example 1:

72 x 11 = 792

Step 1: Split the two digit number and add space between it 7 _ 2

Step 2: Now fill the space by summing 7 & 2 so it will become like 7 9 2. So the answer is 792

Example 2:

67 x 11 = 737

Step 1: Split the two digit number and add space between it 6 _ 7

Step 2: Now fill the space by adding 6 & 7 so it will become  like 6 13 7.

Step 3: Here sum of two digits is 13 so carry forward the 1 to the left side so it will become like 7 3 7. Now the answer is 737.

## Multiply by 5

To quickly multiply any number by 5 follow the below technique

Example 1:

62 x 5 = 310

Step 1: Divide the number by 2. Here 62/ 2 is 31

Step 2: Now multiply by 10. Here 31 x 10 = 310 so is the answer

Here the concept is number 5 is equal to 10/2 and if you notice here I am dividing the 62 by 2 & multiplying by 10

Example 2:

35 x 5 = 175

Step 1: Divide the number by 2. Here 35/ 2 is 17.5

Step 2: Now multiply by 10. Here 17.5 x 10 = 175 so is the answer 🙂

## Multiply by doubling & halving

Here is the another technique for multiplying numbers

Example 1:

70 x 8 = 560

Step 1: Here I am going to double the first number & halve the second number so it becomes 140 x 4

Step 2: Repeat the previous step again so now becomes 280 x 2. Since cannot repeat the same step and even if you do the result is still same 560

This trick works best when halving number is even number else you may end up with decimal numbers