Transcript 2CH6L2
6-2 Estimate with Percents Warm Up Problem of the Day Lesson Presentation Course 2 6-2 Estimate with Percents Warm Up Write each percent as a fraction and as a decimal. 1. 75% 3, 0.75 4 2. 10% 1 , 0.1 10 3. 32% 8 , 0.32 25 4. 17% 17 , 0.17 100 Course 2 6-2 Estimate with Percents Problem of the Day You are biking to the library. When you are 75% of the way there, you realize you forgot a book. So you turn around 1 and head back. When you are of the 3 way back you realize you don’t need the book, so you turn around again and bike 3.2 miles back to the library. How far do you live from the library? 6.4 miles Course 2 6-2 Estimate with Percents Learn to estimate percents. Course 2 6-2 Estimate with Percents The table shows common percents and their fraction equivalents. You can use fractions to estimate the percent of a number by choosing a fraction that is close to a given percent. Percent 10% 20% 25% Fraction 1 10 1 5 1 4 Course 2 1 33 3 % 50% 2 663 % 1 3 1 2 2 3 6-2 Estimate with Percents Additional Example 1: Using Fractions to Estimate Percents Use a fraction to estimate 27% of 63. Think: 27% is about 25% and 1 25% is equivalent to . 4 1 · 60 Change 63 to a compatible 4 number. 15 Multiply. 27% of 63 is about 15. Remember! Compatible numbers are close to the numbers in the problem and are used to do math mentally. 27% of 63 1 · 63 4 Course 2 6-2 Estimate with Percents Try This: Example 1 Use a fraction to estimate 48% of 91. 48% of 91 1 · 91 2 Think: 48% is about 50% and 1 50% is equivalent to . 2 1 · 90 2 Change 91 to a compatible number. 45 Multiply. 48% of 91 is about 45. Course 2 6-2 Estimate with Percents Additional Example 2: Consumer Math Application Cary earns $9.88 per hour. He gets a bonus of 50% for each hour he works overtime. About how much is he paid per hour for overtime? First find the bonus for each hour of overtime. 50% of $9.88 = 1 · $9.88 Think: 50% is equivalent to 1 . 2 2 1 · $10 Change $9.88 to a compatible number. 2 $5 Multiply. The bonus is approximately $5. Since $10 + $5 = $15, he earns about $15 for each hour he works overtime. Course 2 6-2 Insert Lesson Here Estimate with Title Percents Try This: Example 2 Billy has a job assembling office furniture. He is paid $9.20 for each unit completed. If he completes more than 10 units a week he is paid an additional 25% per unit. How much is he paid for each unit above 10. First find the additional amount earned for each unit above 10. 25% of $9.20 = 1· $9.20 Think: 25% is equivalent to 1 . 4 4 Change $9.20 to a compatible 1 · $9 number. 4 $2.25 Multiply. The bonus for each extra unit is approximately $2.25. Since $9 + $2.25 = $11.25, he earns about $11.25 for each extra unit. Course 2 6-2 Estimate with Percents Another way to estimate percents is to find 1% or 10% of a number. You can do this by moving the decimal point in the number. 1% of 45 = .45. 10% of 45 = 45 . . To find 1% of a number, move the decimal point two places to the left. Course 2 To find 10% of a number, move the decimal point one place to the left. 6-2 Estimate with Percents Additional Example 3A: Estimating with Simple Percents Use 1% or 10% to estimate the percent of each number. A. 4% of 18 18 is about 20, so find 4% of 20. 1% of 20 =.20. 4% of 20 = 4 · 0.2 = 0.8 4% equals 4 · 1%. 4% of 18 is about 0.8. Course 2 6-2 Estimate with Percents Additional Example 3B: Estimating with Simple Percents Use 1% or 10% to estimate the percent of each number. B. 29% of 80 29% is about 30, so find 30% of 80. 10% of 80 = 80. . 30% of 80 = 3 · 8.0 = 24.0 30% equals 3 · 10%. 29% of 80 is about 24. Course 2 6-2 Estimate with Percents Try This: Example 3A Use 1% or 10% to estimate the percent of each number. A. 5% of 14 14 is about 15, so find 5% of 15. 1% of 15 =.15. 5% of 15 = 5 · 0.15 = 0.75 5% equals 5 · 1%. 5% of 14 is about 0.75. Course 2 6-2 Estimate with Percents Try This: Example 3B Use 1% or 10% to estimate the percent of each number. B. 21% of 60 21% is about 20, so find 20% of 60. 10% of 60 = 60. . 20% of 60 = 2 · 6.0 = 12.0 20% equals 2 · 10%. 21% of 60 is about 12. Course 2 6-2 Estimate with Percents Additional Example 4: Consumer Math Application Tim spent $58 on dinner for his family. About how much money should he leave for a 15% tip? Since $58 is about $60, find 15% of $60. 15% = 10% + 5% 10% of $60 = $6 5% of $60 = $6 ÷ 2 = $3 $6 + $3 = $9 Think: 15% is 10% + 5%. 1 5% is 2 of 10% so divide $6 by 2. Add the 10% and 5% estimates. Tim should leave about $9 for a 15% tip. Course 2 6-2 Estimate with Percents Try This: Example 4 Amanda spent $12 on a hair cut. About how much money should she leave for a 15% tip. Since $12 is about $10, find 15% of $10. 15% = 10% + 5% 10% of $10 = $1 5% of $10 = $1 ÷ 2 = $0.50 $1 + $0.50 = $1.50 Think: 15% is 10% + 5%. 1 5% is 2 of 10% so divide $1 by 2. Add the 10% and 5% estimates. Amanda should leave about $1.50 for a 15% tip. Course 2 6-2 Estimate Insert Lesson with Percents Title Here Lesson Quiz Use a fraction to estimate the percent of each number. Possible answers: 1. 48% of 72 36 2. 26% of 80 20 Use 1% or 10% to estimate the percent of each number. Possible answers: 3. 4% of 220 8.8 4. 19% of 75 15 5. Mr. and Mrs. Dargen spend $46.25 on a meal. About how much should they leave for a 15% tip? $7 Course 2