Pre-Algebra HOMEWORK

Pre-Algebra

8-2 Finding Percents

Pre-Algebra HOMEWORK

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Spiral Review

Pre-Algebra


Our Learning GoalStudents will be able to determine and construct fractions, decimals, and percents by understanding their relationships, solving for the unknown, solving increase and decrease, solving sales tax/total cost contextual problems and compute simple interest.

Pre-Algebra


Our Learning Goal Assignments

• Learn to relate decimals, fractions, & percents (8-1)

• Learn to find percents (8-2)

• Learn to find a number when the percent is known (8-3)

• Learn to find percent increase and decrease (8-4)

• Learn to estimate with percents (8-5)

• Learn to find commission, sales tax, and withholding tax (8-6)

• Learn to compute simple interest (8-7)

Pre-Algebra

8-2 Finding PercentsLearning Goal Scale

Students are able to determine & construct fractions, decimals, & percents:

4 3 2 1 0

• Clear understanding their relationships

• Able to solve for the unknown

• Understands how to solve for increase & decrease

• Calculating solving sales tax/total cost contextual problems

• Computing simple interest

• Understands their relationships

• Some solving for the unknown

• Difficulty solving for increase & decrease

• Understands their relationships

• Difficulty solving for the unknown

• Some understanding their relationships

• Even with help, no understanding or skill demonstrated

Pre-Algebra

8-2 Finding Percents8-2 Finding Percents

Pre-Algebra

Warm UpWarm Up

Problem of the DayProblem of the Day

Lesson PresentationLesson Presentation

Pre-Algebra


Warm UpRewrite each value as indicated.

1. as a percent

2. 25% as a fraction

3. as a decimal

4. 0.16 as a fraction

48%

0.375

Pre-Algebra


425

24 50

3 8

14

Pre-Algebra


Problem of the Day

A number between 1 and 10 is halved, and the result is squared. This gives an answer that is double the original number. What is the starting number?8

Pre-Algebra


Today’s Learning Goal Assignment

Learn to find percents.

Pre-Algebra


Relative humidity is a measure of the amount of water vapor in the air. When the relative humidity is 100%, the air has the maximum amount of water vapor. At this point, any additional water vapor would cause precipitation. To find the relative humidity on a given day, you would need to find a percent.

Pre-Algebra


Additional Example 1A: Finding the Percent One Number Is of Another

A. What percent of 220 is 88?

Method 1: Set up an equation to find the percent.

p 220 = 88 Set up an equation.

88220

p = Solve for p.

p = 0.4 0.4 is 40%.

So 88 is 40% of 220.

Pre-Algebra


B. Eddie weighs 160 lb, and his bones weigh 24 lb. Find the percent of his weight that his bones are.

Additional Example 1B: Finding the Percent One Number Is of Another

Think: What number is to 100 as 24 is to 160?

=number

100 partwhole Set up a proportion.

Substitute. n

100 24160

=

n 160 = 100 24

160n = 2400

Find the cross products.

Pre-Algebra


Additional Example 1 Continued

n = 15

= 15

100 24160

The proportion is reasonable.

Solve for n.160 2400n =

So 15% of Eddie’s weight is bone.

Pre-Algebra


Try This: Example 1A

A. What percent of 110 is 11?

Method 1: Set up an equation to find the percent.

p 110 = 11 Set up an equation.

11110

p = Solve for p.

p = 0.1 0.1 is 10%.

So 11 is 10% of 110.

Pre-Algebra


B. Jamie weighs 140 lb, and his bones weigh 21 lb. Find the percent of his weight that his bones are.Think: What number is to 100 as 21 is to 140?

=number

100 partwhole Set up a proportion.

Substitute. n

100 21140

=

n 140 = 100 21

140n = 2100

Find the cross products.

Try This: Example 1B

Pre-Algebra


n = 15

The proportion is reasonable.

Solve for n.140 2100n =

So 15% of Jamie’s weight is bone.

= 15

100 21140

Pre-Algebra


Additional Example 2A: Finding a Percent of a Number

A. After a drought, a reservoir had only 66 % of the average amount of water. If the average amount of water is 57,000,000 gallons, how much water was in the reservoir after the drought?

23

Choose a method: Set up an equation.

Think: What number is 66 % of 57,000,000?23

w = 66 % 57,000,000 Set up an equation.23

w = 57,000,000 66 % is equivalent to . 23

23

23

Pre-Algebra


Additional Example 2A Continued

The reservoir contained 38,000,000 gallons of water after the drought.

w = = 38,000,000 114,000,000

3

Pre-Algebra


Additional Example 2B: Finding Percents

B. Ms. Chang deposited $550 in the bank. Four years later her account held 110% of the original amount. How much money did Ms. Chang have in the bank at the end of the four years?

Choose a method: Set up a proportion.

=110

100 a

550Set up a proportion.

110 550 = 100 a Find the cross products.

60,500 = 100a

Pre-Algebra


Additional Example 2B Continued

605 = a Solve for a.

Ms. Chang had $605 in the bank at the end of the four years.

Pre-Algebra



A. After a drought, a river had only 50 % of the average amount of water flow. If the average amount of water flow is 60,000,000 gallons per day, how much water was flowing in the river after the drought?

23

Choose a method: Set up an equation.

Think: What number is 50 % of 60,000,000?23

w = 50 % 60,000,000 Set up an equation.23

w = 0.506 60,000,000 50 % is equivalent to 0.506. 23

Pre-Algebra



The water flow in the river was 30,400,000 gallons per day after the drought.

w = 30,400,000

Pre-Algebra


Try This: Example 2B

B. Mr. Downing deposited $770 in the bank. Four years later his account held 120% of the original amount. How much money did Mr. Downing have in the bank at the end of the four years?

Choose a method: Set up a proportion.

=120

100 a

770 Set up a proportion.

120 770 = 100 a Find the cross products.

92,400 = 100a

Pre-Algebra


Try This: Example 2B Continued

924 = a Solve for a.

Mr. Downing had $924 in the bank at the end of the four years.

Pre-Algebra


Lesson Quiz

Find each percent to the nearest tenth.

1. What percent of 33 is 22?

2. What percent of 300 is 120?

3. 18 is what percent of 25?

4. The volume of Lake Superior is 2900 mi3 and

the volume of Lake Erie is 116 mi3. What percent

of the volume of Lake Superior is the volume of

Lake Erie?

40%

66.7%

72%

4%

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Pre-Algebra HOMEWORK