# Working backwards with percentages

• Mar 6th 2010, 04:17 PM
MikeChch
Working backwards with percentages
There is one type of question to do with percentages that I just can't get my head around. Below is an example:

Staff at a computer game store get a discount of 21% on games. Bill bragged to his parents that he saved $102 last year. How much did Bill spend last year on games? I have been given the answer as$383.71 but for the life of me I can't work out how they got it.

• Mar 6th 2010, 04:57 PM
Quote:

Originally Posted by MikeChch
There is one type of question to do with percentages that I just can't get my head around. Below is an example:

Staff at a computer game store get a discount of 21% on games. Bill bragged to his parents that he saved $102 last year. How much did Bill spend last year on games? I have been given the answer as$383.71 but for the life of me I can't work out how they got it.

Hi Mike,

The amount that he saved is 21% of total.

The amount he spent was 79% of total.

1% of total is

$\frac{102}{21}$

79% of total is

$\frac{102(79)}{21}$