1. Holt CA Course 1 6-4 Percent of a Number 6-4 Percent of a Number NS1.4 Calculate given percentages of quantities and solve problems involving discounts at sales, interest earned, and tips. Also covered: NS2.4 California Standards

2. Holt CA Course 1 6-4 Percent of a Number The human body is made up mostly of water. In fact, about 67% of a person’s total (100%) body weight is water. If Cameron weighs 90 pounds, about how much of his weight is water? Recall that a percent is a part of 100. Since you want to know the part of Cameron’s body that is water, you can set up and solve a proportion to find the answer. Part 67 = nPart 100 90 Whole

3. Holt CA Course 1 6-4 Percent of a Number Find the percent of each number. Additional Example 1: Using Proportions to Find Percents of Numbers A. 30% of 50 30 100 = n 50 30 · 50 = 100 · n 1,500 = 100n 1,500 100 = 100n 15 = n 30% of 50 is 15. Write a proportion. Set the cross products equal. Multiply. Divide each side by 100.

4. Holt CA Course 1 6-4 Percent of a Number When solving a problem with a percent greater than 100%, the part will be greater than the whole. Helpful Hint

5. Holt CA Course 1 6-4 Percent of a Number Additional Example 1: Using Proportions to Find Percents of Numbers Find the percent of each number. B. 200% of 24 200 100 = n 24 200 · 24 = 100 · n 4,800 = 100n 4,800 100 = 100n 48 = n 200% of 24 is 48. Write a proportion. Set the cross products equal. Multiply. Divide each side by 100.

6. Holt CA Course 1 6-4 Percent of a Number Find the percent of each number. Check It Out! Example 1 A. 40% of 40 40 100 = n 40 40 · 40 = 100 · n 1,600 = 100n 1,600 100 = 100n 16 = n 40% of 40 is 16. Write a proportion. Set the cross products equal. Multiply. Divide each side by 100.

7. Holt CA Course 1 6-4 Percent of a Number Check It Out! Example 1 Find the percent of each number. B. 150% of 64 150 100 = n 64 150 · 64 = 100 · n 9,600 = 100n 9,600 100 = 100n 96 = n 150% of 64 is 96. Write a proportion. Set the cross products equal. Multiply. Divide each side by 100.

8. Holt CA Course 1 6-4 Percent of a Number In addition to using proportions, you can find a percent of a number by using decimal equivalents.

9. Holt CA Course 1 6-4 Percent of a Number Find the percent of the number. Check whether your answer is reasonable. Additional Example 2: Using Decimal Equivalents to Find Percents of Numbers A. 9% of 80 9% of 80 = 0.09 · 80 = 7.2 Check Since 10% of 80 = 8, a reasonable answer for 9% of 80 is 7.2. Write the percent as a decimal and multiply. 0 20% 40% 60% 80% 100% 0 60 80 20 40 9% 7.2

10. Holt CA Course 1 6-4 Percent of a Number Additional Example 2: Using Decimal Equivalents to Find Percents of Numbers Find the percent of the number. Estimate to check whether your answer is reasonable. B. 3% of 12 3% of 12 = 0.03 · 12 = 0.36 Check 5% · 12 = 0.6, so 3% of 12 is a little less than 0.6. Thus 0.36 is a reasonable answer. Write the percent as a decimal and multiply.

11. Holt CA Course 1 6-4 Percent of a Number Find the percent of the number. Check whether your answer is reasonable. Check It Out! Example 2 A. 21% of 40 21% of 40 = 0.21 · 40 = 8.4 Check Since 20% of 40 = 8, a reasonable answer for 21% of 40 is 8.4. Write the percent as a decimal and multiply. 0 20% 40% 60% 80% 100% 0 30 40 10 20 21% 8.4

12. Holt CA Course 1 6-4 Percent of a Number Check It Out! Example 2 Find the percent of the number. Estimate to check whether your answer is reasonable. B. 6% of 18 6% of 18 = 0.06 · 18 = 1.08 Check 5% · 20 = 1, so 6% of 18 is close to 1. Thus 1.08 is a reasonable answer. Write the percent as a decimal and multiply.

13. Holt CA Course 1 6-4 Percent of a Number Additional Example 3: Geography Application The estimated world population in 2001 was 6,157 million. About 40% of the people were 19 or younger. What was the approximate number of people 19 or younger, to the nearest million? Find 40% of 6,157 million. 0.40 · 6,157 = 2,462.8 The number of people 19 or younger was about 2,463 million. Write the percent as a decimal. Multiply. ≈ 2,463Round to the nearest whole number.

14. Holt CA Course 1 6-4 Percent of a Number Check It Out! Example 3 The estimated world population in 2001 was 6,157 million. About 60% of the people were above 19 years of age. What was the approximate number of people 19 or older, to the nearest million? Find 60% of 6,157 million. 0.60 · 6,157 = 3,694.2 The number of people 19 or older was about 3,694 million. Write the percent as a decimal. Multiply. ≈ 3,694Round to the nearest whole number.