Percents of Increase and Decrease

Percentages & Percentages Increase/Decrease

Dr. Tom Giles

Percentages

Daily Percentages Use

-Calculating a grade

-MONEY

-Leaving a tip at a restaurant

-Sales and Discounts

-Commission

-Sales Tax and Interest

Basic Percentage Facts

-Percent = "Per 100" always out of 100

Percents and Decimals:

-Percent to Decimal (divide by 100%)

-Decimal to Percent (multiply by 100%)

Percents and Fractions:

-Percent to Fraction (write over 100%)

-Fraction to Percent (divide numerator by denominator & multiply by 100%)

Multiple Choice

What is 35% as a decimal?

• 35

• 3.5

• 0.35

• 0.035

Multiple Choice

What is 8% as a decimal?

• 8

• 0.8

• 0.08

• 80

Multiple Choice

What is 0.46 as a percent?

• 46%

• 4.6%

• 0.46%

• 460%

Multiple Choice

What is 0.04 as a percent?

• .4%

• 4%

• 40%

• 400%

Using Percents

To find the percent of a number or amount you need to:

1. Write the percent as a decimal (divide by 100%)

2. Multiply by the number or amount

Multiple Choice

What is 5% of 16?

• 8

• 0.8

• 80

• 11

Multiple Choice

What is 20% of 64?

• 128

• 1.28

• 12.8

• 44

Multiple Choice

Sales tax is __________ to the price

• subtracted

• added

• multipled

• divided

Calculating Grades

How to find your percentage of a grade:

-take the points you earned (top number) and divide by the total points possible (bottom number) and multiply by 100%

Example: You took a Math test and scored 37 points out of 50. What is your percentage?

Multiple Choice

On last night's homework, you scored a 10 out of 12. What is your percentage on this homework assignment?

• 80%

• 10%

• 120%

• 83.3%

Multiple Choice

On your quick check, you scored a 7 out of 8. What is your percentage on this quick check?

• 87.5%

• 114%

• 7%

• 70%

Calculating a Tip Amount

Example: You are out to eat with your family at Boondock Eddie's. The total bill was $42.50. If you want to leave a 20% tip, how much money should you leave?

Multiple Choice

Bill:  $25
Percentage of tip:  20%
Tip????

• $6.00

• $5.00

• $2.50

• $4.00

Multiple Choice

You are having dinner at Mi Casitas. Your bill is $60.85. You want to leave a tip amount of 20%, how much money should you leave for the tip?

• $40.85

• $20

• $12.17

• $15.68

Percentage Increase & Decrease

Percentage Increase & Decrease

​Percent Increase: Add the % increase to 100% and multiply by the original amount.

Percent Decrease: Subtract the % decrease from 100% and multiply by the original amount.

Multiple Choice

Discount is ____________ from the price.

The resulting price is lower than the original price.

• subtracted

• added

• multipled

• divided

DISCOUNT TIME

Example: You go to Dollar Tree and want to buy something that costs $50. You have a coupon for 15% off. How much will you have to pay after the discount?

Multiple Choice

You go to Walmart and want to buy a video game for $30. You have a coupon for 10% off. How much do you have to pay after the coupon discount?

• $20

• $27

• $29

• $33

Multiple Choice

You go to Ellis & Chapman's to buy some clothes. You have a coupon for 30% off. If your total is $67, how much will you pay with the coupon?

• $37.00

• $20.10

• $46.90

• $64.00

Multiple Choice

A pair of boots is $94.99.  They are 25% off. With this discount, what is the sale price? Round to the nearest cent if necessary.

• $71.24

• $118.74

• 23.7475

• $23.75

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