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2-10 Percent Increase and Decrease Warm Up 1. Find 30% of 40. 12 2. Find 28% of 60. 16.8 Solve for x. 3. 22 = x(50) 0.44 4. 17.2 = x(86) 38 5. 20 is what percent of 80? 25% 6. 36 is what percent of 30? 120% Holt Algebra 1 2-10 Percent Increase and Decrease Objective Find percent increase and decrease. Holt Algebra 1 2-10 Percent Increase and Decrease A percent change is an increase or decrease given as a percent of the original amount. Percent increase describes an amount that has grown and percent decrease describes an amount that has be reduced. Holt Algebra 1 2-10 Percent Increase and Decrease Example 1A: Finding Percent Increase and Decrease Find each percent change. Tell whether it is a percent increase or decrease. From 8 to 10 Simplify Simplifythe thenumerator. fraction. = 0.25 Write the answer as a percent. = 25% 8 to 10 is an increase, so a change from 8 to 10 is a 25% increase. Holt Algebra 1 2-10 Percent Increase and Decrease Example 1B: Finding Percent Increase and Decrease Find the percent change. Tell whether it is a percent increase or decrease. From 75 to 30 Simplify Simplifythe thefraction. numerator. = 0.6 Write the answer as a percent. = 60% 75 to 30 is a decrease, so a change from 75 to 30 is a 60% decrease. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 1a Find each percent change. Tell whether it is a percent increase or decrease. From 200 to 110 Simplify numerator. Simplify thethe fraction. = 0.6 Write the answer as a percent. = 60% 200 to 110 is an decrease, so a change from 200 to 110 is a 60% decrease. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 1b Find each percent change. Tell whether it is a percent increase or decrease. From 25 to 30 Simplifythe thefraction. numerator. Simplify = 0.20 Write the answer as a percent. = 20% 25 to 30 is an increase, so a change from 25 to 30 is a 20% increase. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 1c Find each percent change. Tell whether it is a percent increase or decrease. From 80 to 115 Simplifythe thefraction. numerator. Simplify = 0.4375 = 43.75% Write the answer as a percent. 80 to 115 is an increase, so a change from 80 to 115 is a 43.75% increase. Holt Algebra 1 2-10 Percent Increase and Decrease Example 2: Finding Percent Increase and Decrease A. Find the result when 12 is increased by 50%. Find 50% of 12. This is the amount of increase. It is a percent increase, so add 6 to 12 + 6 =18 the original amount. 12 increased by 50% is 18. B. Find the result when 55 is decreased by 60%. Find 60% of 55. This is the amount of 0.60(55) = 33 decrease. It is a percent decrease so subtract 55 – 33 = 22 33 from the the original amount. 0.50(12) = 6 55 decreased by 60% is 22. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 2 A. Find the result when 72 is increased by 25%. Find 25% of 72. This is the amount of increase. It is a percent increase, so add 18 to 72 + 18 =90 the original amount. 72 increased by 25% is 90. B. Find the result when 10 is decreased by 40%. Find 40% of 10. This is the amount of 0.40(10) = 4 decrease. It is a percent decrease so subtract 4 10 – 4 = 6 from the the original amount. 0.25(72) = 18 10 decreased by 40% is 6. Holt Algebra 1 2-10 Percent Increase and Decrease Common application of percent change are discounts and markups. A discount is an discount = % of original price amount by which an original price is final price = original price – discount reduced. A markup is an markup = % of wholesale cost amount by which a wholesale price final price = wholesale cost + markup is increased. Holt Algebra 1 2-10 Percent Increase and Decrease Example 3: Discounts The entrance fee at an amusement park is $35. People over the age of 65 receive a 20% discount. What is the amount of the discount? How much do people over 65 pay? Method 1 A discount is a percent decrease. So find $35 decreased by 20%. 0.20(35) = 7 35 – 7 = 28 Holt Algebra 1 Find 20% of 35. This is the amount of the discount. Subtract 7 from 35. This is the entrance fee for people over the age of 65. 2-10 Percent Increase and Decrease Example 3A: Discounts Method 2 Subtract the percent discount from 100%. 100% – 20% = 80% 0.80(35) = 28 35 – 28 = 7 People over the age of 65 pay 80% of the regular price, $35. Find 80% of 35. This is the entrance fee for people over the age of 65. Subtract 28 from 35. This is the amount of the discount. By either method, the discount is $7. People over the age of 65 pay $28.00. Holt Algebra 1 2-10 Percent Increase and Decrease Example 3B: Discounts A student paid $31.20 for art supplies that normally cost $52.00. Find the percent discount . Think: 20.80 is what $52.00 – $31.20 = $20.80 percent of 52.00? Let x 20.80 = x(52.00) represent the percent. Since x is multiplied by 52.00, divide both sides by 52.00 to undo the 0.40 = x multiplication. 40% = x The discount is 40% Holt Algebra 1 Write the answer as a percent. 2-10 Percent Increase and Decrease Check It Out! Example 3a A $220 bicycle was on sale for 60% off. Find the sale price. Method 2 Subtract the percent discount from 100%. 100% – 60% = 40% 0.40(220) = 88 The bicycle was 60% off of 100% . Find 40% of 220. By this method, the sale price is $88. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 3b Ray paid $12 for a $15 T-shirt. What was the percent discount ? $15 – $12 = $3 3 = x(15) 0.20 = x 20% = x The discount is 20%. Holt Algebra 1 Think: 3 is what percent of 15? Let x represent the percent. Since x is multiplied by 15, divide both sides by 15 to undo the multiplication. Write the answer as a percent. 2-10 Percent Increase and Decrease Example 4: Markups The wholesale cost of a DVD is $7. The markup is 85%. What is the amount of the markup? What is the selling price? Method 2 1 A markup is a percenttoincrease. Add percent markup 100% So find $7 increased by 85%. Find 85% of 7. This is the amount The selling price is 185% of the 100% 0.85(7)+=85% 5.95= 185% of the markup. wholesale price, 7. Find 185% of 7. is the selling 1.85(7) 7 + 5.95==12.95 12.95 Add to 7. This is This the selling price. price. 12.95 7 = 5.95 Subtract from 12.95. This is the amount of the markup. By either method, the amount of the markup is $5.95. The selling price is $12.95. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 4 A video game has a 70% markup. The wholesale cost is $9. What is the selling price? Method 1 A markup is a percent increase. So find $9 increased by 70%. 0.70(9) = 6.30 Find 70% of 9. This is the amount of the markup. 9 + 6.30 = 15.30 Add to 9. This is the selling price. The amount of the markup is $6.30. The selling price is $15.30. Holt Algebra 1 2-10 Percent Increase and Decrease Check It Out! Example 4 What is the percent markup on a car selling for $21,850 that had a wholesale cost of $9500? 21,850 – 9,500 = 12,350 12,350 = x(9,500) 1.30 = x 130% = x Find the amount of the markup. Think: 12,350 is what percent of 9,500? Let x represent the percent. Since x is multiplied by 9,500 divide both sides by 9,500 to undo the multiplication. Write the answer as a percent. The markup was 130 percent. Holt Algebra 1 2-10 Percent Increase and Decrease Lesson Quiz: Part 1 Find each percent change. Tell whether it is a percent increase or decrease. 1. from 20 to 28. 40% increase 2. from 80 to 62. 22.5% decrease 3. from 500 to 100. 80% decrease 4. find the result when 120 is increased by 40%. 168 5. find the result when 70 is decreased by 20%. Holt Algebra 1 56 2-10 Percent Increase and Decrease Lesson Quiz: Part 2 Find each percent change. Tell whether it is a percent increase or decrease. 6. A movie ticket costs $9. On Mondays, tickets are 20% off. What is the amount of discount? How much would a ticket cost on a Monday? $1.80; $7.20 7. A bike helmet cost $24. The wholesale cost was $15. What was the percent of markup? 60% Holt Algebra 1 2-10 Percent Increase and Decrease Home work pg. 141 16-34 evens 46,48,58,60,62 Holt Algebra 1