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8-2. Finding Percents. Warm Up. Problem of the Day. Lesson Presentation. Pre-Algebra. 8-2. Finding Percents. 24. 50. 4. 1. 25. 4. 3. 8. Pre-Algebra. Warm Up Pssa Tested Rewrite each value as indicated. 1. as a percent 2. 25% as a fraction 3. as a decimal

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8-2

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  1. 8-2 Finding Percents Warm Up Problem of the Day Lesson Presentation Pre-Algebra

  2. 8-2 Finding Percents 24 50 4 1 25 4 3 8 Pre-Algebra • Warm Up Pssa Tested • Rewrite each value as indicated. • 1. as a percent • 2. 25% as a fraction • 3. as a decimal • 4. 0.16 as a fraction 48% 0.375

  3. objective for today Learn to find percents.

  4. Finding the Percent One Number Is of Another What percent of 220 is 88?

  5. Finding the Percent One Number Is of Another What percent of 19 is 95?

  6. Finding the Percent One Number Is of Another 18 is what percent of 60?

  7. Practice Problems! What percent of 102 is 17? 13 is what percent of 52?

  8. number part 100 = whole 24 n = 160 100 Finding the Percent One Number Is of Another Eddie weighs 160 lb, and his bones weigh 24 lb. Find the percent of his weight that his bones are. Method 2: Set up a proportion to find the percent. Think:What number is to 100 as 24 is to 160? Set up a proportion. Substitute. n 160 = 100 24 Find the cross products. 160n = 2400

  9. 2400 n = 160 15 24 = 100 160 Additional Example 1 Continued Solve for n. n = 15 The proportion is reasonable. So 15% of Eddie’s weight is bone.

  10. number part 100 = whole 21 n = 140 100 Try This: Example 1B B. Jamie weighs 140 lb, and his bones weigh 21 lb. Find the percent of his weight that his bones are. Method 2: Set up a proportion to find the percent. Think:What number is to 100 as 21 is to 140? Set up a proportion. Substitute. n 140 = 100 21 Find the cross products. 140n = 2100

  11. 2100 n = 140 15 21 = 100 140 Solve for n. n = 15 The proportion is reasonable. So 15% of Jamie’s weight is bone.

  12. A. After a drought, a reservoir had only 66 % of the average amount of water. If the average amount of water is 57,000,000 gallons, how much water was in the reservoir after the drought? 2 2 2 2 3 3 3 3 Think:What number is 66 % of 57,000,000? w = 66 % 57,000,000 Set up an equation. w = 57,000,000 66 % is equivalent to . 2 2 3 3 Additional Example 2A: Finding a Percent of a Number Choose a method: Set up an equation.

  13. 114,000,000 3 w = = 38,000,000 Additional Example 2A Continued The reservoir contained 38,000,000 gallons of water after the drought.

  14. Set up a proportion. = 110 a 100 550 Additional Example 2B: Finding Percents B. Ms. Chang deposited $550 in the bank. Four years later her account held 110% of the original amount. How much money did Ms. Chang have in the bank at the end of the four years? Choose a method: Set up a proportion. 110  550 = 100 a Find the cross products. 60,500 = 100a

  15. Additional Example 2B Continued 605 = a Solve for a. Ms. Chang had $605 in the bank at the end of the four years.

  16. Set up a proportion. = 120 a 100 770 Try This: Example 2B B. Mr. Downing deposited $770 in the bank. Four years later his account held 120% of the original amount. How much money did Mr. Downing have in the bank at the end of the four years? Choose a method: Set up a proportion. 120 770 = 100 a Find the cross products. 92,400 = 100a

  17. Try This: Example 2B Continued 924 = a Solve for a. Mr. Downing had $924 in the bank at the end of the four years.

  18. Let's Review! What percent of 88 is 13? 90 is what percent of 75? What percent of 4 is 6?

  19. Lesson Quiz Find each percent to the nearest tenth. 1. What percent of 33 is 22? 2. What percent of 300 is 120? 3. 18 is what percent of 25? 4. The volume of Lake Superior is 2900 mi3 and the volume of Lake Erie is 116 mi3. What percent of the volume of Lake Superior is the volume of Lake Erie? 66.7% 40% 72% 4%

  20. Question Time Help!

  21. What we learned today! Learned to find percents.

  22. Assignment Complete page 407 in your text

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