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Warm Up Problem of the Day Lesson Presentation Lesson Quizzes
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Write each decimal as a percent and fraction.
Warm Up Write each decimal as a percent and fraction. 3. 0.2 19 50 __ 38%, 3 50 __ 6%, 1 5 __ 20%,
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Problem of the Day Lucky Jim won $16,000,000 in a lottery. Every year for 10 years he spent 50% of what was left. How much did Lucky Jim have after 10 years? $15,625
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Sunshine State Standards
MA.6.A.5.1 Use equivalent forms of fractions, decimals, and percents to solve problems. Also MA.6.A.5.3
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To find the percent one number is of another, use this proportion:
% 100 = is of Because you are looking for 45% of 420, 45 replaces the percent sign and 420 replaces “of.” The first denominator, 100, always stays the same. The “is” part is what you have been asked to find.
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Additional Example 1: Application
There are 560 students in Ella’s school. If 35% of the students participate in after-school sports, how many students participate in after- school sports? First estimate your answer. Think: 35% = , which is close to , and 560 is close to 600. So about of the students participate in after-school sports. 35 100 ___ 1 3 __ 1 3 __ • 600 = 200 This is the estimate. Helpful Hint Think: “35 out of 100 is how many out of 560?”
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Additional Example 1 Continued
Now solve: Let s represent the number of students who participate in after- school sports. 35 100 ___ s 560 ___ = 100 • s = 35 • 560 The cross products are equal. 100s = 19,600 s is multiplied by 100. 100s 100 ____ 19,600 100 _____ Divide both sides of the equation by 100 to undo multiplication. = s = 196 Since 196 is close to your estimate of 200, 196 is a reasonable answer. 196 students participate in after-school sports.
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Check It Out: Example 1 There are 480 students in Tisha’s school. If 70% of the students participate in the fundraising program, how many students participate is that ? 70 100 ___ x 480 ___ = ; 100x = 33,600; x = 336 students
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Additional Example 2: Application
Johan is 25% of the way through his exercises. If he has exercised for 20 minutes so far, how much longer does he have to work out? 25% of the exercises are completed, so 20 minutes is 25% of the total time needed. % 100 ___ is of __ = Set up a proportion. The “of” part is what you have been asked to find. 25 100 ___ 20 m __ = 100 • 20 = 25 • m The cross products are equal.
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Additional Example 2 Continued
m is multiplied by 25. 2,000 25 _____ 25m 25 ____ Divide both sides by 25 to undo multiplication. = 80 = m The time needed for the exercises is 80 min. So far, the exercises have taken 20 min. Because – 20 = 60, Johan will be finished in 60 min.
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Check It Out: Example 2A Katie has read 35% of a book. If she has read 49 pages, how many more pages does Katie have left to read? 35 100 ___ 49 p __ = ; 35p = 4,900; p = 140 pages = 91 pages
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Check It Out: Example 2B Justin is 75% through washing and folding his laundry. If he has finished 6 loads, how many loads does he still need to do? 75 100 ___ 6 l __ = ; 75 l = 600; l = 8 loads 8 - 6 = 2 loads
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Instead of using proportions, you can also multiply to find a percent of a number.
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Additional Example 3: Multiplying to Find a Percent of a Number
Find 36% of 50. 36% = 0.36 Write the percent as a decimal. 0.36 • 50 Multiply using the decimal. 18 So 18 is 36% of 50. Check Use a model to check the answer. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
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Check It Out: Example 3A Find the percent of each number. 20% of 140 0.2 • 140 = 28
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Check It Out: Example 3B Find the percent of each number. 45% of 900 0.45 • 900 = 405
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Check It Out: Example 3C Find the percent of each number. 80% of 30 0.8 • 30 = 24
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Check It Out: Example 3D Find the percent of each number. 15% of 150 0.15 • 150 = 22.5
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Check It Out: Example 3E Find the percent of each number. 75% of 360 0.75 • 360 = 270
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Check It Out: Example 3F Find the percent of each number. 30% of 170 0.3 • 170 = 51
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Lesson Quizzes Standard Lesson Quiz Lesson Quiz for Student Response Systems
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Lesson Quiz 1. Find 28% of 310. 2. Find 70% of 542. 3. Martha is taking a 100-question test. She has completed 60% of the test in 45 minutes. How much longer will it take her to finish the test? 4. Crystal has a collection of 72 pennies. If 25% of them are Canadian, how many Canadian pennies does she have? 86.8 379.4 30 min 18
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Lesson Quiz for Student Response Systems
1. Identify 35% of 260. A B. 91 C D. 295
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Lesson Quiz for Student Response Systems
2. Identify 60% of 422. A B. 482 C D
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Lesson Quiz for Student Response Systems
3. Ella has to draw a flowchart as a part of an assignment. She has drawn 40% of the flowchart in 10 minutes. How much longer will it take her to complete the flowchart? A. 10 min B. 25 min C. 15 min D. 35 min
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Lesson Quiz for Student Response Systems
4. Of 80 sheep in a field, 65% are ewes. How many ewes are there in the field? A. 28 ewes B. 52 ewes C. 65 ewes D. 108 ewes
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