Holt McDougal Algebra Percent Increase and Decrease Warm Up 1. Find 30% of Find 28% of 60. Solve for x = x(50) = x(86) is what percent of 80? is what percent of 30? % 120%

Holt McDougal Algebra Percent Increase and Decrease Use common applications of percents Find percent increase and decrease. Objective

Holt McDougal Algebra Percent Increase and Decrease A commission is money paid to a person or a company for making a sale. Usually the commission is a percent of the sale amount.

Holt McDougal Algebra Percent Increase and Decrease Example 1 Mr. Cortez earns a base salary of $26,000 plus a sales commission of 5%. His total sales for one year were $300,000. Find his total pay for the year. Write the formula for total pay. total pay = base salary + commission Write the formula for commission. Substitute values given in the problem. = 26, % of 300,000 = base + % of total sales Write the percent as a decimal. = 26,000 + (0.05)(300,000) Multiply.= 26, ,000 Add.= 41,000 Mr. Cortez’s total pay was $41,000.

Holt McDougal Algebra Percent Increase and Decrease Interest is the amount of money charged for borrowing money, or the amount of money earned when saving or investing money. Principal is the amount borrowed or invested. Simple interest is interest paid only on the principal. Simple Interest Paid Annually Time in years Interest rate per year as a decimal Principal Simple interest

Holt McDougal Algebra Percent Increase and Decrease Example 2 Find the simple interest paid for 3 years on a $2500 loan at 11.5% per year. I = Prt Write the formula for simple interest. I = (2500)(0.115)(3) Substitute known values. Write the interest rate as a decimal. I = The amount of interest is $ Multiply.

Holt McDougal Algebra Percent Increase and Decrease Example 3 After 6 months, the simple interest earned on an investment of $5000 was $45. Find the interest rate. I = Prt Write the formula for simple interest. 45 = 2500r = r The interest rate is 1.8%. Substitute the given values. Multiply Since r is multiplied by 2500, divide both sides by 2500 to undo the multiplication.

Holt McDougal Algebra 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 McDougal Algebra Percent Increase and Decrease Example 4 Find each percent change. Tell whether it is a percent increase or decrease. From 8 to 10 = 0.25 = 25% Write the answer as a percent. Simplify the numerator.Simplify the fraction. 8 to 10 is an increase, so a change from 8 to 10 is a 25% increase.

Holt McDougal Algebra Percent Increase and Decrease From 75 to 30 = 0.6 = 60% Write the answer as a percent. Simplify the numerator.Simplify the fraction. 75 to 30 is a decrease, so a change from 75 to 30 is a 60% decrease. Example 5 Find the percent change. Tell whether it is a percent increase or decrease.

Holt McDougal Algebra Percent Increase and Decrease Example 6 A. Find the result when 12 is increased by 50%. 0.50(12) = 6 Find 50% of 12. This is the amount of increase =18 It is a percent increase, so add 6 to the original amount. 12 increased by 50% is 18. B. Find the result when 55 is decreased by 60%. 0.60(55) = 33 Find 60% of 55. This is the amount of decrease. 55 – 33 = 22 It is a percent decrease so subtract 33 from the the original amount. 55 decreased by 60% is 22.

Holt McDougal Algebra Percent Increase and Decrease Example 7 Method 1 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 Find 20% of 35. This is the amount of the discount. 35 – 7 = 28 Subtract 7 from 35. This is the entrance fee for people over the age of 65.

Holt McDougal Algebra Percent Increase and Decrease Example 7 Method 2 Method 2 Subtract the percent discount from 100%. 100% – 20% = 80% People over the age of 65 pay 80% of the regular price, $ (35) = 28 Find 80% of 35. This is the entrance fee for people over the age of – 28 = 7 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 McDougal Algebra Percent Increase and Decrease Example 8 A student paid $31.20 for art supplies that normally cost $ Find the percent discount. $52.00 – $31.20 = $20.80 Think: is what percent of 52.00? Let x represent the percent = x(52.00) 0.40 = x 40% = x The discount is 40% Since x is multiplied by 52.00, divide both sides by to undo the multiplication. Write the answer as a percent.

Holt McDougal Algebra Percent Increase and Decrease Example 9 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 = Add to 9. This is the selling price. The amount of the markup is $6.30. The selling price is $15.30.

Holt McDougal Algebra Percent Increase and Decrease  You must complete 10 notecards  Answers must be completed on a separate sheet of paper  The final answer will be on the back of the notecard  Homework: Page  3-33 (multiples of 3)  (multiples of 5)  Start when finished 10 notecards

Holt McDougal Algebra Percent Increase and Decrease Exit Card 1. from 20 to from 80 to from 500 to find the result when 120 is increased by 40%. 5. find the result when 70 is decreased by 20%. Find each percent change. Tell whether it is a percent increase or decrease.

Holt McDougal Algebra Percent Increase and Decrease Exit Card: 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? 7. A bike helmet cost $24. The wholesale cost was $15. What was the percent of markup?

Holt McDougal Algebra Percent Increase and Decrease Exit Card 1. from 20 to from 80 to from 500 to find the result when 120 is increased by 40%. 5. find the result when 70 is decreased by 20%. Find each percent change. Tell whether it is a percent increase or decrease. 40% increase 22.5% decrease 80% decrease

Holt McDougal Algebra Percent Increase and Decrease Exit Card: 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? 7. A bike helmet cost $24. The wholesale cost was $15. What was the percent of markup? $1.80; $ %