Gre math Review 1 Arithmetic

1.7 Percent

The term percent means per hundred, or hundredths. Percents are ratios that are often used to represent parts of a whole, where the whole is considered as having 100 parts. Here are three examples of percents.

Example A: 1 percent means 1 part out of 100 parts, or   1 over 100.
Example B: 32 percent means 32 parts out of 100 parts, or   32 over 100.
Example C: 50 percent means 50 parts out of 100 parts, or   1 half.

Note that the part is the numerator of the ratio and the whole is the denominator. Percents are often written with the % symbol; fractional and decimal equivalents are often used as well but without the % symbol, as in the following five example.

Example A:   1% = 1 over 100, which is equal to 0.01
Example B:   100% = 100 over 100, which is equal to 1.
Example C:  32% = 32 over 100, which is equal to 0.32
Example D:   50% = 50 over 100, which is equal to 0.5
Example E:  0.3% = 0.3 over 100, which is equal to 0.003

Be careful not to confuse 0.01 with 0.01%. The percent symbol matters. For example,  

0.01 = 1% but 0.01% = 0.01 over 100, which is equal to 0.0001.

To compute a percent, given the part and the whole, divide the part by the whole. The result will be the decimal equivalent, so multiply the result by 100 to convert to percent.

Example 1.7.1: If the whole is 20 and the part is 13, you can find the percent as follows.

 

part over whole = 13 over 20, which is equal to 0.65, or 65%.

Example 1.7.2: What percent of 150 is 12.9 ?

Solution: Here the whole is 150 and the part is 12.9, so

 

part over whole = 12.9 over 150, which is equal to 0.086, or 8.6%.

To find the