Algebra 1 Companion Book, Vol 1 – Summer Edition

2.2.3 Percents

Key Objectives • Use proportions to solve percent problems. • Use equations to solve percent problems. • Write equations to solve percent problems for the part, percent, or whole. Key Terms • A percent is a ratio of a number to 100. A percent is a ratio that compares a number to 100. For example, 25% is equal to 25:100.

To find the fraction equivalent of a percent, write the percent as a ratio with a denominator of 100. Then simplify the fraction, if possible. For example, 25% = 25/100 = 1/4. So, the fraction equivalent of 25% is 1/4. To find the decimal equivalent of a percent, divide the percent by 100. For example, 75% = 75/100 = 0.75. So, the decimal equivalent of 75% is 0.75. The decimal equivalent of 100% is 100/100, or 1. Percents can be greater than 100%. For example, 120% = 120/100 = 1.2. Percents can also be less than 1%. For example, 0.5% = 0.5/100 = 0.005. The following proportion relates the percent to the ratio of a specific amount, or part, to the whole. It can be used to find an unknown value (part, whole, or percent).

part whole

percent 100


Example 1 Finding the Part In Example 1, Prof. Burger uses two methods (using a proportion and translating into an equation) to find a percent of a number.


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