Algebra 1 Section 3.4

Definition A percent is a ratio of a number to one hundred. The symbol for percent is %. Percents can be written with the symbol, as fractions, or as decimals.

Example 1 82% = 82 100 = 41 50 82% = 0.82

Example 2 = 3 5 0.6 0.6(100%) = 60%

Example 3 1.55(100%) = 155% 155% = 155 100 = 31 20

The percent of the whole is equal to the part: The Percent Equation The percent of the whole is equal to the part: percent × whole = part

Example 4 What percent of 85 is 17? p × 85 = 17 p = 17 85 = 0.2

Example 5 What is 45% of 236? r = 0.45(236) r = 106.2

Example 6 78 is 130% of what number? 1.3w = 78 w = 78 1.3 = 60

Example 7 2% of the milk is butterfat. 0.02m = 1 m = 1 0.02 = 50 50 gal of 2% milk contains 1 gal of butterfat.

What percent of the votes did Miss Grandy receive? Example 8 What percent of the votes did Miss Grandy receive? What percent of 31,800 is 17,490? p × 31,800 = 17,490

Yes, she won the election. Example 8 p × 31,800 = 17,490 p = 17,490 31,800 = 0.55 p = 0.55(100%) = 55% Yes, she won the election.

Homework: pp. 114-116