Find the Whole
The word percent (per + cent) means per 100. The symbol % looks like its meaning /100. You can replace the % symbol in any problem with /100.
There are 3 general types of percent problems which you'll often encounter.
- Find the part (also called the percentage).
- Find the rate.
- Find the whole (also called the base).
Let's look at the third type: Find the whole. Here's an example problem: 20% of
what number is $12?
For this, it helps to look at the whole described in terms of the part and the
rate. Recall that P = W • R. If we divide both sides of this equation by R we
get that
W = P/R where W is the whole, P is the part, and R is the Rate.
The Whole is equal to the Part divided by the rate. In this problem, the whole is unknown but we know the part and the rate. The part is $12 and the rate is 20%. So the whole must be $12 divided by 20%. I.e., 12 ÷ 0.2 = 60, so the whole, W = $60. In summary, 20% of $60 is $12.
Now try it on your own!
Find the whole.
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