Question

If a = 12 and 120% of a is equal to 80\% of bthen what is a + b ?

Answer 1

The answer is 30

Explanation:

First you have to find 120% of a (12).

`(12)/(1) * (120)/(100) = 14.4`

Therefore; 14.4 is 80% of b, and we are trying to find 100% of b

`14.4 = 80\% \\ x = 100\%`

we do not know what is 100% therefore we call it *x*. In order to find this unknown value *x* we cross multiply.

`14.4 * 100\% = 80\% * x`

This is the same as saying;

`14.4 * 1 = x * (4)/(5)`

100% percent would be 1 because it is the whole number we are trying to find. The 80% would be 4/5. To get 4/5 you can simply break down 80/100 ( this is 80% as a fraction).

so the new equation is: 14.4= 4/5x

We divide both sides by 4/5. Then we will get x tobe equal to 18. Therefore b is 18. We were asked to find (a + b) so. 18+12 = 30