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Math 8 Lesson 2.2

Math 8 Lesson 2.2. Rates. Definitions and Examples. A rate is a comparison of two quantities measured in different units Eg $5 dollars for 20 apples 120km per two hours A unit rate is a rate in which the second term is one Eg . 120km/2hours  60km/1 hour or 60km/ hr. Example 1.

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Math 8 Lesson 2.2

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  1. Math 8 Lesson 2.2 Rates

  2. Definitions and Examples • A rate is a comparison of two quantities measured in different units • Eg $5 dollars for 20 apples • 120km per two hours • A unit rate is a rate in which the second term is one • Eg. 120km/2hours 60km/1 hour or 60km/hr

  3. Example 1 • Johnny runs a 10 km race in 45 minutes – this is a rate • This reduces to 2km/9mins (divide both by 5 to get lowest term) • The unit rate is … • 2/9 km/min= 0.2 km/min but we need to change to km/ 1 hour Multiply 60 both top and bottom to get 13.3 km/hr (use 60 to convert minutes to hours because 60 minutes = 1 hour

  4. Definitions and Examples A unit price is a unit rate in which the first term is measured in $ or ¢. Example 2: Lemons are sold at a rate of 99¢ for 3 lemons or $3.60 for a dozen. What is the better deal? 99¢ for 3 lemons has a unit price of 33¢/lemon (99÷3) $3.60 for a dozen (12) has a unit price of … $0.30 per lemon = 30¢/lemon therefore $3.60/dozen is a better deal

  5. Last example P.58 in textbook Consider the salsa being sold in the following three sizes for the price listed below each container. What is the best deal on salsa? $3.44 for 425mL has a unit price of… $0.008094117/mL convert it to litres for ease $8.094117/L (multiply by 1000 as there are 1000 mL per L) $6.29for 642mL has a unit price of…. $0.0097975/mL or $9.7975/L $15.49 for 1.7L has a unit price of $9.11764/L The best deal then is the smallest jar as it has the lowest unit price

  6. Your task Questions 1 and 2 page 59 Questions 4-12 pp. 60-61

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