[Reverse Percentages] Reverse calculate original amount given a percentage #math

reverse-percentages.txt

1. Add or subtract the percentage given in the problem from 100% to determine what percentage we have.
2. Find 1% by dividing by the percentage found in the previous step.
3. Find 100% (original amount) by multiplying your answer in step 2 by 100.

<100% Example:
A shop is having a sale where all items are 30% off. 
An item is on sale for $84.
What was the original price of the item?

100% - 30% = 70% of the original price
$84 = 70%
$84 / 70 = $1.20 (or 1% of the original price)
$1.20 * 100 = $120 (the original price)

>100% Example:
After a 4% wage rise, Bill earned $1248 each month.
How much did Bill earn each month before the wage rise?

100% + 4% = 104% of the original price
$1248 = 104%
$1248 / 104 = $12 (or 1% of the original price)
$12 * 100 = $1200 (the original price)