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Objective : Finding Unit Rates Finding Unit Prices to Compare Costs

SOL 7.4, 8.3a Use measures expressed as rates (e.g., speed, density) and measures expressed as products (e.g., person-days) to solve problems; check the units of the solutions; and use dimensional analysis to check the reasonableness of the answer. Objective : Finding Unit Rates

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Objective : Finding Unit Rates Finding Unit Prices to Compare Costs

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  1. SOL 7.4, 8.3a Use measures expressed as rates (e.g., speed, density) and measures expressed as products (e.g., person-days) to solve problems; check the units of the solutions; and use dimensional analysis to check the reasonableness of the answer. Objective: Finding Unit Rates Finding Unit Prices to Compare Costs

  2. Rate Movie

  3. Notes A rate is a comparison of two quantities measured in different units. 90 3 Ratio: Read as “90 miles per 3 hours.” 90 miles 3 hours Rate:

  4. 90 3 The ratio can be simplified by dividing: Notes Unit rates are rates in which the second quantity is 1. 90 3 30 1 = 30 miles, 1 hour unit rate: or 30 mi/h

  5. Check It Out! Example 1 Penelope can type 90 words in 2 minutes. How many words can she type in 1 minute? 90 words 2 minutes Write a rate. Divide to find words per minute. 90 words ÷ 2 2 minutes ÷ 2 45 words 1 minute = Penelope can type 45 words in one minute.

  6. 455 students 91 computers 468 students 91 computers  5 students 1 computer  Additional Example 3A: Estimating Unit Rates Estimate each unit rate. 468 students to 91 computers Choose a number close to 468 that is divisible by 91. Divide to find students per computer. 468 students to 91 computers is approximately 5 students per computer.

  7. 595 players 85 soccer balls 583 players 85 soccer balls  7 players 1 soccer ball  Check It Out! Example 3A Estimate each unit rate. 583 soccer players to 85 soccer balls. Choose a number close to 583 that is divisible by 85. Divide to find players per soccer ball. 583 soccer players to 85 soccer balls is approximately 7 players per soccer ball.

  8. Pactice • Estimate each unit rate • 121 students in 3 buses • 31.50 for 4 hours

  9. Unit price is a unit rate used to compare price per item.

  10. Additional Example 4A: Finding Unit Prices to Compare Costs Pens can be purchased in a 5-pack for $1.95 or a 15-pack for $6.20. Which pack has the lower unit price? Divide the price by the number of pens. price for package number of pens $1.95 5 = = $0.39 price for package number of pens $6.20 15 =  $0.41 The 5-pack for $1.95 has the lower unit price.

  11. price for bottle number of ounces price for bottle number of ounces Check It Out!Example 4B John can buy a 24 oz bottle of ketchup for $2.19 or a 36 oz bottle for $3.79. Which bottle has the lower unit price? Divide the price by the number of ounces. $2.19 24 =  $0.09 $3.79 36 =  $0.11 The 24 oz jar for $2.19 has the lower unit price.

  12. Lesson Quiz: Part I 1. Meka can make 6 bracelets per half hour. How many bracelets can she make per hour? 2. A penny has a mass of 2.5 g and a volume of approximately 0.360 cm3. What is the approximate density of a penny? Estimate each unit rate. 3. $2.22 for 6 stamps 4. 8 heartbeats in 6 seconds 12 ≈ 6.94 g/cm3 $0.37 per stamp 1.3 beats/s

  13. Lesson Quiz: Part II Find each unit price. Then tell which has the lower unit price. 5. A half dozen carnations for $4.75 or a dozen for $9.24 6. 4 pens for $5.16 or a ten-pack for $12.90. a dozen They cost the same.

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