7-7 Percents Course 1 Warm Up Problem of the Day Lesson Presentation

Write each fraction as a decimal. 1. 2. Warm Up Write each fraction as a decimal. 1. 2. Write each decimal as a fraction. 3. 0.375 4. 0.05 3 4 __ 9 10 __ 0.75 0.9 3 8 __ 1 20 __

Problem of the Day Wally wanted to change the scale of a drawing from 1 in. = 2 ft to 1 in. = 10 ft. The scale height of a building in the first drawing is 25 in. How high is the building in the new drawing? 5 in.

Learn to write percents as decimals and as fractions.

Vocabulary percent

Most states charge sales tax on items you purchase Most states charge sales tax on items you purchase. Sales tax is a percent of the item’s price. A percent is a ratio of a number to 100. You can remember that percent means “per hundred.” For example, 8% means “8 per hundred,” or “8 out of 100.”

If a sales tax rate is 8%, the following statements are true: For every $1.00 you spend, you pay $0.08 in sales tax. For every $10.00 you spend, you pay $0.80 in sales tax. For every $100 you spend, you pay $8 in sales tax. Because percent means “per hundred,” 100% means “100 out of 100.” This is why 100% is often used to mean “all” or “the whole thing.”

Additional Example 1: Modeling Percent Use a 10-by-10-square grid to model 17%. A 10-by-10 square grid has 100 squares. 17% means “17 out of 100” or . 17 100 ___ Shade 17 squares out of 100 squares.

Check It Out: Example 1 Use a 10-by-10-square grid to model 26%. A 10-by-10 square grid has 100 squares. 26% means “26 out of 100” or . 26 100 ___ Shade 26 squares out of 100 squares.

Additional Example 2: Writing Percents as Fractions Write 35% as a fraction in simplest form. 35 100 ___ Write the percent as a fraction with a denominator of 100. 35% = 35 ÷ 5 100 ÷ 5 _______ 7 20 __ = Write the fraction in simplest form. 7 20 __ Written as a fraction, 35% is .

Check It Out: Example 2 Write 65% as a fraction in simplest form. 65 100 ___ Write the percent as a fraction with a denominator of 100. 65% = 65 ÷ 5 100 ÷ 5 _______ 13 20 __ = Write the fraction in simplest form. 13 20 __ Written as a fraction, 65% is .

Additional Example 3: Life Science Application Janell has 20% body fat. Write 20% as a fraction in simplest form. 20 100 ___ Write the percent as a fraction with a denominator of 100. 20% = 20 ÷ 20 100 ÷ 20 _______ 1 5 __ = Write the fraction in simplest form. 1 5 __ Written as a fraction, 20% is .

Check It Out: Example 3 Timmy has 14% body fat. Write 14% as a fraction in simplest form . 14 100 ___ Write the percent as a fraction with a denominator of 100. 14% = 14 ÷ 2 100 ÷ 2 _______ 7 50 __ = Write the fraction in simplest form. 7 50 __ Written as a fraction, 14% is .

Additional Example 4: Writing Percents as Decimals Write 56% as a decimal. 56 100 ___ Write the percent as a fraction with a denominator of 100. 56% = 100 56.00 0.56 –500 600 –600 Write the fraction as a decimal. Written as a decimal, 56% is 0.56. To divide by 100, move the decimal point two places to the left. 56 ÷ 100 = 0.56 Remember!

Check It Out: Example 4 Write 32% as a decimal. 32 100 ___ Write the percent as a fraction with a denominator of 100. 32% = 100 32.00 0.32 –300 200 –200 Write the fraction as a decimal. Written as a decimal, 32% is 0.32.

Additional Example 5: Application Water made up 85% of the fluids that Kirk drank yesterday. Write 85% as a decimal. 85 100 ___ Write the percent as a fraction with a denominator of 100. 85% = 85 ÷ 100 = 0.85 Write the fraction as a decimal. Written as a decimal, 85% is 0.85.

Check It Out: Example 5 Water made up 95% of the fluids that Lisa drank yesterday. Write 95% as a decimal. 95 100 ___ Write the percent as a fraction with a denominator of 100. 95% = 95 ÷ 100 = 0.95 Write the fraction as a decimal. Written as a decimal, 95% is 0.95.

Lesson Quiz Write each percent as a fraction in simplest form. 1. 52% 2. 29% Write each percent as a decimal. 3. 17% 4. 86% 5. A store clerk has an 8% sales increase. Write the increase as a fraction in simplest form and as a decimal. 13 25 __ 29 100 ___ 0.17 0.86 2 25 __ , 0.08