Percent of Change Lesson 7.5 OBJ: To find the percent of change in a quantity.

Percent of ChangePercent of Change

Lesson 7.5Lesson 7.5

OBJ: To find the percent of OBJ: To find the percent of change in a quantity. change in a quantity.


Indicates how much a quantity Indicates how much a quantity increases or decreases with respect increases or decreases with respect to the original amount. to the original amount.

If the new amount is greater than the If the new amount is greater than the original amount than it is a percent original amount than it is a percent of increase. of increase.

If the new amount is less than the If the new amount is less than the original amount than it is a percent original amount than it is a percent of decrease. of decrease.


The percent of change is the ratio of The percent of change is the ratio of the amount of increase or decrease the amount of increase or decrease to the original amount. to the original amount.

Percent of change or Percent of change or p% = p% = Amount of increase or decreaseAmount of increase or decrease

original amount original amount

Find the percent of increase Find the percent of increase

1.1. Original: 20; New: 25Original: 20; New: 25



Find the Percent of Find the Percent of DecreaseDecrease




Finding a New AmountFinding a New Amount

If you know the original amount and If you know the original amount and the percent of change, you can find the percent of change, you can find the new amount. First multiply the the new amount. First multiply the percent of change by the original percent of change by the original amount to find the amount of amount to find the amount of change. Then increase or decrease change. Then increase or decrease the original amount by the amount of the original amount by the amount of change. change.

ExamplesExamples

Increase 45 by 20%Increase 45 by 20% 20% x 45 = .20 x 45 20% x 45 = .20 x 45

= 9= 9

45 + 9 = 5445 + 9 = 54

Decrease 85 by Decrease 85 by 28%28%

28% x 85 = .28 x 28% x 85 = .28 x 85 = 23.885 = 23.8

85 – 23.8 = 61.285 – 23.8 = 61.2

More ExamplesMore Examples

1.1. At its first visit to a veterinarian, a At its first visit to a veterinarian, a puppy weighted 28 pounds. Three puppy weighted 28 pounds. Three months later, the puppy weighed 46 months later, the puppy weighed 46 pounds. Find the percent of pounds. Find the percent of increase in its weight. increase in its weight.

2.2. Find the percent of decrease from Find the percent of decrease from 250 to 149. 250 to 149.

ExamplesExamples

3.3. An annual concert was attended by 4212 An annual concert was attended by 4212 people last year. This year, the number people last year. This year, the number attending increased by about 14% over attending increased by about 14% over last year. How many people attended the last year. How many people attended the concert this year? concert this year?

4.4. Last month, a restaurant charged $12.95 Last month, a restaurant charged $12.95 for a seafood pasta dinner. This month, for a seafood pasta dinner. This month, the owner has new menus printed, wit all the owner has new menus printed, wit all dinner prices increase by 12%. What is dinner prices increase by 12%. What is the new price for the seafood pasta the new price for the seafood pasta dinner? dinner?

HomeworkHomework

Text p. 355-356, #’s 7-21all Text p. 355-356, #’s 7-21all problems. You must show all work. problems. You must show all work.

Percent of Change Lesson 7.5 OBJ: To find the percent of change in a quantity.

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