Understanding Percentages in Pre-Algebra: A Comprehensive Review
This educational material provides a detailed review of using percentages in pre-algebra, covering key concepts such as finding percentages of numbers like 80, understanding the relationships between different percentages, and practical applications such as calculating tips. Each scenario is explained visually and step-by-step, making it easier to grasp the concept of percentages.
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ALA: Pre-Algebra Unit 5 Percentages Unit 5 Review Flashcards
In your head: What is... 100% of 80?
100% is the WHOLE THING: X + X 100% of 80 is 80
In your head: What is... 200% of 80?
200% is the twice the whole: X + X 200% of 80 is 160
In your head: What is... 50% of 80?
50% is half: X + X 50% of 80 is 40
In your head: What is... 25% of 80?
25% is one-fourth: X + X 25% of 80 is 20
In your head: What is... 10% of 80?
10% is one-tenth, so move the decimal one spot to the left: X + X 10% of 80 is 8
In your head: What is... 20% of 80?
20% is twice as much as 10%: X + X 20% of 80 is 16
In your head: What is... 15% of 80?
15% is halfway between 10% and 20%: X + X 15% of 80 is 12
The meal cost $12.00 What is a 20% tip? X + X
The meal cost $12.00 X + X 10% of $12.00 is $1.20. Double that to get 20%, so the tip would be $2.40.
The meal cost $25.00 A coupon gives you 20% off. X + X How much will you pay?
10% of 25 is $2.50. So 20% of 25 is double that, or $5. You ll save X + X $5, so you ll pay $20.
10 is 50% of what number?
One way: 50% means half. 10 is half of 20. Another way: Set up a proportion 50 = 10 50x = 1000, so x = 20. 100 x Another way: set up an equation 10 = 50% of x 10 = .5x x = 10/.5 = 20
10 is what percent of 50?
One way: set up a proportion 50x = 1000, so x = 20. 10 is 20% of 50. 100 50 x = 10 X + X Another way: equation 10 = x 50 so x = .2, which is 20%
What is 40% of 150?
In your head: 10% of 150 is 15. 40% is 4 times that much, or 4 x 15 = 60. Another way: proportion 40 = x 100x = 6000 so x = 60. 100 150 Another way: equation 40% of 150 = x, so .4(150) = x, so x = 60.
1.3% of children are allergic to peanuts. In a pediatric hospital with 2000 patients a year, how many would you expect to have X + X peanut allergies?
You could set up a proportion: 1.3 = x 100 2000 100x = 2600, so X + X x = 26 kids allergic to peanuts.
30% of Americans have hay fever. Of those, 75% find over-the-counter allergy medications helpful. How many people in a town of 1200 would have hay fever that was NOT helped by over-the-counter medication?
30% of 1200 is 360 people with hay fever. 75% of these 360, or of them, ARE helped by over-the-counter meds. That s 270 who ARE helped by the medicine. That leaves 360 270, or 90 people, who are NOT helped. X + X
Change the percent to a decimal and a fraction: 43%
Change the percent to a decimal and a fraction: 43% = .43 = 43 100
Change the percent to a decimal and a fraction: 135%
Change the percent to a decimal and a fraction: 135% = 1.35 = 135 = 27 100 20
Change the percent to a decimal and a fraction: .6%
Change the percent to a decimal and a fraction: .6% = .006 = 6 = 3 1000 500
Change the decimal to a fraction and a percent: .6
Change the decimal to a fraction and a percent: .6 = 6 = 3 = 60% 10 5
Change the decimal to a fraction and a percent: .07
Change the decimal to a fraction and a percent: .07 = 7 = 7% 100
Change the fraction to a decimal and a percent: 3 8
Change the fraction to a decimal and a percent: 3 = .375 = 37.5% 8
You are done with the ALA Unit 5 Review
Resources: Picture on slides 2, 4, 6, 8, 12, 14, 16, 18 Thinking Man by is licensed under CC BY-SA 4.0 Picture on slide 16 and 17 Pasta salad closeup by Brynn is licensed under CC BY-SA 3.0 Picture on slide 18 and 19 Som tam thai by Takeaway is licensed under CC BY-SA 3.0 Picture on slides 26 and 27 No Peanuts Allergy Alert Pendant by BeInspiredDesigns is licensed under CC BY-NC 2.0; Cropped from original work. MoHealthWINs This workforce solution was funded by a grant awarded by the U.S. Department of Labor s Employment and Training Administration. The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership. Unless otherwise noted this MoHealthWINs material by St. Louis Community College is licensed under a Creative Commons Attribution 4.0 International License.
