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Math humor:

Math humor: Wow! 9 out of 10 cars this company has built in the past 20 years are still on the road. Amazing. Except that the company just started manufacturing cars last year. Vocabulary A rate is a comparison of two quantities measured in different units. 90 3. Ratio:. Read as

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Math humor:

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  1. Math humor: Wow! 9 out of 10 cars this company has built in the past 20 years are still on the road. Amazing. Except that the company just started manufacturing cars last year.

  2. Vocabulary 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:

  3. 90 3 The ratio can be simplified by dividing: 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

  4. 30 words minute 1 2 30 words • 2 minute • 2 1 2 Example 1: Finding Unit Rates Geoff can type 30 words in half a minute. How many words can he type in 1 minute? Write a rate. Multiply to find words per minute. 60 words 1 minute = Geoff can type 60 words in one minute.

  5. Example 2 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. Talking Example: Chemistry Application Five cubic meters of copper has a mass of 44,800 kilograms. What is the density of copper? 44,800 kg 5 m3 Write the rate. 44,800 kg ÷ 5 5 m3 ÷ 5 Divide to find kilograms per 1 m3. 8,960 kg 1 m3 Copper has a density of 8,960 kg/m3.

  7. Talking Example: Chemistry Application A piece of gold with a volume of 0.5 cubic meters weighs 9650 kilograms. What is the density of gold? 9650 kg 0.5 m3 Write the rate. 9650 kg • 2 0.5 m3 • 2 Multiply to find kilograms per 1 m3. 19,300 kg 1 m3 Gold has a density of 19,300 kg/m3.

  8. 455 students 91 computers 468 students 91 computers  5 students 1 computer  Talking Example: 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.

  9. 320 feet 8 seconds 313 feet 8 seconds  40 feet 1 second  Talking Example: Estimating Unit Rates Estimate each unit rate. 313 feet in 8 seconds Choose a number close to 313 that is divisible by 8. Divide to find feet per second. 313 feet to 8 seconds is approximately 40 feet per second.

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

  11. Example 3A: 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.

  12. price for jar number of ounces price for jar number of ounces Example 3B: Finding Unit Prices to Compare Costs Jamie can buy a 15 oz jar of peanut butter for $2.19 or a 20 oz jar for $2.78. Which jar has the lower unit price? Divide the price by the number of ounces. $2.19 15 =  $0.15 $2.78 20 =  $0.14 The 20 oz jar for $2.78 has the lower unit price.

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