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Pre-Algebra

Learn to find percents. 8-2. Finding Percents. Pre-Algebra. 8-2. Finding Percents. Pre-Algebra.

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Pre-Algebra

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  1. Learn to find percents. 8-2 Finding Percents Pre-Algebra

  2. 8-2 Finding Percents Pre-Algebra Relative humidity is a measure of the amount of water vapor in the air. When the relative humidity is 100%, the air has the maximum amount of water vapor. At this point, any additional water vapor would cause precipitation. To find the relative humidity on a given day, you would need to find a percent.

  3. 88 8-2 Finding Percents p = Solve for p. 220 Pre-Algebra Example 1A: Finding the Percent One Number Is of Another A. What percent of 220 is 88? Method 1: Set up an equation to find the percent. p220 = 88 Set up an equation. p = 0.4 0.4 is 40%. So 88 is 40% of 220.

  4. number n part 8-2 Finding Percents 24 = = 100 100 whole 160 Pre-Algebra Example 1B: Finding the Percent One Number Is of Another B. Sam 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

  5. 15 2400 24 8-2 Finding Percents n = = 160 100 160 Pre-Algebra Example 1B Continued Solve for n. n = 15 The proportion is reasonable. So 15% of Sam’s weight is bone.

  6. 2 2 2 2 2 2 8-2 Finding Percents w = 57,000,000 66 % is equivalent to . w = 66 % 57,000,000 Set up an equation. Think:What number is 66 % of 57,000,000? 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? 3 3 3 3 3 3 Pre-Algebra Example 2A: Finding a Percent of a Number Choose a method: Set up an equation.

  7. 114,000,000 8-2 Finding Percents w = = 38,000,000 3 Pre-Algebra Example 2A Continued The reservoir contained 38,000,000 gallons of water after the drought.

  8. 110 a 8-2 Finding Percents Set up a proportion. = 100 550 Pre-Algebra Example 2B: Finding Percents B. Sarah deposited $550 in the bank. Four years later her account held 110% of the original amount. How much money did Hannah 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

  9. 8-2 Finding Percents Pre-Algebra Example 2B Continued 605 = a Solve for a. Sarah had $605 in the bank at the end of the four years.

  10. 11 8-2 Finding Percents p = Solve for p. 110 Pre-Algebra Try This: Example 1A A. What percent of 110 is 11? Method 1: Set up an equation to find the percent. p110 = 11 Set up an equation. p = 0.1 0.1 is 10%. So 11 is 10% of 110.

  11. number n part 8-2 Finding Percents 21 = = 100 100 whole 140 Pre-Algebra Try This: Example 1B B. Matt 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

  12. 15 2100 21 8-2 Finding Percents n = = 140 100 140 Pre-Algebra Solve for n. n = 15 The proportion is reasonable. So 15% of Matt’s weight is bone.

  13. 2 2 2 2 8-2 Finding Percents Think:What number is 50 % of 60,000,000? w = 50 % 60,000,000 Set up an equation. A. After a drought, a river had only 50 % of the average amount of water flow. If the average amount of water flow is 60,000,000 gallons per day, how much water was flowing in the river after the drought? w = 0.506 60,000,000 50 % is equivalent to 0.506. 3 3 3 3 Pre-Algebra Try This: Example 2A Choose a method: Set up an equation.

  14. 8-2 Finding Percents Pre-Algebra Try This: Example 2A w = 30,400,000 The water flow in the river was 30,400,000 gallons per day after the drought.

  15. 120 a 8-2 Finding Percents Set up a proportion. = 100 770 Pre-Algebra Try This: Example 2B B. Anthony deposited $770 in the bank. Four years later his account held 120% of the original amount. How much money did Anthony 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

  16. 8-2 Finding Percents Pre-Algebra Try This: Example 2B Continued 924 = a Solve for a. Anthony had $924 in the bank at the end of the four years.

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