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# Unit Rates

May 12, 2015

## Education

Solving rates in Alge

#### unit rate amy

• 1.Unit Rates

2. Vocabulary

• Arateis a ratio that compares two quantities measured in different units.
• Theunit rateis the rate for one unit of a given quantity.Unit rates have a denominator of 1.

3. Examples Rate: 150 heartbeats 2 minutes Unit Rate (Divide to get it): 150 2 = 75 heartbeats per minute. 4. Find the Unit Rate Amy can read 88 pages in 4 hours.What is the unit rate? (How many pages can she read per hour?) 88 pages 4 hours 22 pages / hour 5. Using Unit Rates

• You can find the missing terms of equal ratios.
• Use the unit rate, and set it equal to another ratio.
• Solve for what is missing by dividing or multiplying.

6. Example Joes car goes 25 miles per gallon of gasoline.How far can it go on 8 gallons of gasoline? 25 miles 1 gallon Unit Rate = 8 gallons x 8 x 8 25 x 8 = 200.Joes car can go 200 miles on 8 gallons of gas. 7. Comparing Unit Prices

• Use division to find the unit prices of the two products in question.
• The unit rate that is smaller (costs less) is the better value.

8. Example Juice is sold in two different sizes.A 48-fluid ounce bottle costs \$2.07.A 32-fluid ounce bottle costs \$1.64.Which is the better buy? \$2.07 48 fl.oz. \$0.04 per fl.oz. \$1.64 32 fl.oz. \$0.05 per fl.oz. The 48 fl.oz. bottle is the better value. 9. Rate of Work Problems 10. Marge can clean the house in 3 hrs. Lisa can clean it in 5 hrs. How long will it take them to clean the house if they both work together? 11. Use Unit Rates Marge can clean the house in 3 hrs.,so she does1 / 3of the house per hour. 12. Use Unit Rates Lisa can clean the house in 5 hrs.,so she does1 / 5of the house per hour. 13. LetTbe the time in hours. 1 3 T + 1 5 T = 1 14. 1 / 3 T +1 / 5 T = 1 15( 1 / 3 T +1 / 5 T) = 15(1) 5T + 3T = 15 8T = 15 T =15 / 8 1 7 / 8hrs. 15. Bart can wash the car in 20 min. Homer can wash it in 30 min. How long will it take them to wash the car if they both work together? 16. Use Unit Rates Bart can wash the car in 20 min.,so he does1 / 20of the car per min. 17. Use Unit Rates Homer can wash the car in 30 min.,so he does1 / 30of the car per min. 18. LetMbe the time in minutes. 1 20 M + 1 30 M = 1 19. 1 / 20 M +1 / 30 M = 1 60( 1 / 20 M +1 / 30 M) = 60(1) 3M + 2M = 60 5M = 60 M = 12 min. 20. Springfield School 21. Mr. Skinner can enroll 15 students per hr. Mr. Chalmer can enroll 20 students per hr. How long will it take them to enroll 140 students working together? 22. Use Unit Rates Minutes work better than hours. Mr. Skinner enrolls 15 students per 60 min.,so he enrolls15 / 60or1 / 4students per min. 23. Use Unit Rates Minutes work better than hours. Mr. Chalmer enrolls 20 students per 60 min.,so he enrolls20 / 60or1 / 3students per min. 24. 1 / 4 M +1 / 3 M = 140 12( 1 / 4 M +1 / 3 M) = 12(140) 3M + 4M = 1680 7M = 1680 M = 240 min.= 4 hrs. 25. Grading Papers 26. Mrs. Krabappel can grade a set of papers in 1 1 / 2hrs. Miss Hoover can grade them in 80 min. How long will it take them to grade one set if they both work together? 27. Use Unit Rates Minutes work better than hours. Mrs. Krabappel grades1 / 90of a set per min. 28. Use Unit Rates Miss Hoover grades1 / 80of a set per min. 29. 1 / 90 M +1 / 80 M = 1 720( 1 / 90 M +1 / 80 M) = 720(1) 8M + 9M = 720 17M = 720 M = 42 6 / 17min. 30. Approximately how long would it take them to grade 3 sets if they both work together? 31. 1 / 90 M +1 / 80 M = 3 720( 1 / 90 M +1 / 80 M) = 720(3) 8M + 9M = 2160 17M = 2160 M = 127 1 / 17min.A little more than 2 hrs. 32. Math Is Fun