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Warm Up 1. 14,000 is 2 % of what number? 2. 39 is 13% of what number? 3. 37 % of what number is 12? 4. 150% of what number is 189? 560,000 300 32 1 2 126 1 2

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Lesson 2 Percent Increase and Decrease

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Percents can be used to describe a change. Percent of change is the ratio of the amount of change to the original amount. Percent of increase describes how much the original amount increases. Percent of decrease describes how much the original amount decreases. amount of change original amount percent of change =

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Find the percent of increase or decrease from 16 to 12. Class Example This is a percent of decrease. 16 – 12 = 4First find the amount of change. amount of decrease original amount 4 16 Set up the ratio. Find the decimal form. Write as a percent. = 0.25 = 25% 4 16 From 16 to 12 is a 25% decrease.

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Find the percent increase or decrease from 45 to 54. This is a percent of increase. 54 – 45 = 9First find the amount of change. amount of increase original amount 9 45 Set up the ratio. Partner Practice Find the decimal form. Write as a percent. = 0.20 = 20% 9 45 From 45 to 54 is a 20% increase.

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Find the percent increase or decrease from 50 to 65. This is a percent of increase. Individual Practice 65 – 50 = 15First find the amount of change. amount of increase original amount 15 50 Set up the ratio. Find the decimal form. Write as a percent. = 0.30 = 30% 15 50 From 50 to 65 is a 30% increase.

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When Jim was exercising, his heart rate went from 72 beats per minute to 98 beats per minute. What was the percent increase to the nearest tenth of a percent? Class Example 26 72 Set up the ratio. 98 – 72 = 26 First find the amount of change. amount of increase original amount Find the decimal form. Write as a percent. 0.361 36.1% 26 72 From 72 to 98 increases by about 36.1%.

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In 2005, a certain stock was worth $1.25 a share. In 2006, the same stock was worth $0.85 a share. What was the percent decrease? Individual Practice 1.25 – 0.85 = 0.40 First find the amount of change. amount of decrease original amount 1.25 0.40 Set up the ratio. Find the decimal form. Write as a percent. = 0.32 = 32% 1.25 0.40 The value of the stock decreased by 32%.

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Discount is the difference between the regular price and the sale price of an item. You can use percent of decrease to find discounts. Markup is the difference between the wholesale cost and the retail price of an item. You can use percent of increase to find markups.

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Sarah bought a DVD player originally priced at $450 that was on sale for 20% off. What was the discounted price? Practice (450)(0.20) = 90Find 20% of $450. This is the amount of discount. 450 – 90 = 360Subtract $90 from $450. Method 2: Subtract, then multiply. 100% – 20% = 80%Find the percent Sarah pays. Method 1: Multiply, then subtract. (450)(0.80) = 360Find 80% of 450. The discounted price was $360.

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