PERCENTS
with 0. The 50th digit is 3.
27 . Identifying the Parts and the Whole
The key to solving most fraction and percent word problems is to identify the part and the
whole. Usually you’ll find the part associated with the verb is/are and the whole associated
with the word of. In the sentence “Half of the boys are blonds,” the whole is the boys (“of the
boys”), and the part is the blonds (“are blonds”).
28 . Percent Formula
Whether you need to find the part, the whole, or the percent, use the same formula:
Part = Percent × Whole
Example: What is 12 percent of 25?
Setup: Part = 0.12 × 25.
Example: 15 is 3 percent of what number?
Setup: 15 = 0.03 × Whole.
Example: 45 is what percent of 9?
Setup: 45 = Percent × 9.
29 . Percent Increase and Decrease
To increase a number by a percent, add the percent to 100 percent, convert to a decimal, and
multiply. To increase 40 by 25 percent, add 25 percent to 100 percent, convert 125 percent to
1.25, and multiply by 40. 1.25 × 40 = 50.
30 . Finding the Original Whole
To find the original whole before a percent increase or decrease, set up an equation. Think
of the result of a 15 percent increase over x as 1.15x.
Example: After a 5 percent increase, the population was 59,346. What was the population
before the increase?
