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 Vocabulary: Percent of a Number

3. 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

4. Holt CA Course 1 6-4 Percent of a Number Find the percent of each number. Teacher 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.

5. 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

6. Holt CA Course 1 6-4 Percent of a Number Teacher 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.

7. Holt CA Course 1 6-4 Percent of a Number Find the percent of each number. Student Practice 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.

8. Holt CA Course 1 6-4 Percent of a Number Student Practice 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.

9. 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.

10. Holt CA Course 1 6-4 Percent of a Number Find the percent of the number. Check whether your answer is reasonable. Teacher 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

11. Holt CA Course 1 6-4 Percent of a Number Teacher 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.

12. Holt CA Course 1 6-4 Percent of a Number Find the percent of the number. Check whether your answer is reasonable. Student Practice 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

13. Holt CA Course 1 6-4 Percent of a Number Student Practice 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.

14. Holt CA Course 1 6-4 Percent of a Number Teacher Example 3: Consumer Math Write the percent as a decimal. Multiply. Round to the nearest whole number. Show Style is discounting everything in the store by 25%. What is the sale price of a pair of flip-flops that was originally priced at $10?

15. Holt CA Course 1 6-4 Percent of a Number Student Practice 3: Write the percent as a decimal. Multiply. Round to the nearest whole number. A store that sells sports souvenirs is offering a 30% discount on all items. The tags on the items show the original prices. Find the amount of discount On the figurine shown.

16. Holt CA Course 1 6-4 Percent of a Number Lesson Quiz Find the percent of each number. 1. 25% of 8 2. 40% of 110 Find the percent of each number. Check whether your answer is reasonable. 3. 150% of 96 4. 0.3% of 120 5. Whitmer Middle School has 850 students. If 42% of the students bought lunch on Monday, how many student bought lunch on Monday? 44 2 144 0.36 357