pre-algebra homework
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Pre-Algebra HOMEWORK. Page 407 #17-27 & Spiral Review. Our Learning Goal. - PowerPoint PPT PresentationTRANSCRIPT
Pre-Algebra
8-2 Finding Percents
Pre-Algebra HOMEWORK
Page 407
#17-27 &
Spiral Review
Pre-Algebra
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
425
24 50
3 8
14
Pre-Algebra
8-2 Finding Percents
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
8-2 Finding Percents
Today’s Learning Goal Assignment
Learn to find percents.
Pre-Algebra
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
n = 15
The proportion is reasonable.
Solve for n.140 2100n =
So 15% of Jamie’s weight is bone.
= 15
100 21140
Pre-Algebra
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
Try This: Example 2A
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
8-2 Finding Percents
Try This: Example 2A
The water flow in the river was 30,400,000 gallons per day after the drought.
w = 30,400,000
Pre-Algebra
8-2 Finding Percents
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
8-2 Finding Percents
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
8-2 Finding Percents
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%