To find 10% of a number we must find 1/10 of it.
One way to do this is to divide the number by 10.
To find 20% of a number we first find 10% and then double the result.
Example
Find 20% of 530
Answer
First we find 10% which is 530 ÷ 10 = 53
Then we double the result to get 53 x 2 = 106