Comparing CD Prices

7-2 Rates

Turn and Talk

• What would you do with $1000?• What if you had to share it with your

group?• What if you had to share it with your

class?• $1000/26 people• That is a rate---it compares 2 quantities

with different units. What are some other rates?

• The ads use rates to describe sale prices. To compare prices in sales such as these, it’s often useful to find a unit rate. A Unit Rate is a rate in which one of the numbers being compared is 1 unit.

CD SALE!!!!

5 for 49.95

HUGE SAVINGS!!! All discs on sale!

7 for $65.80

• The comparisons “45 miles per gallon,” “$3.50 per hour,” “8.5 kilometers per hour,” and “two sandwiches for each person” are all unit rates. “Per gallon” means “for one gallon” and “per hour” means “for one hour.”

• Which store has the lower price per CD?

CD SALE!!!!

5 for 49.95

HUGE SAVINGS!!! All discs on sale!

7 for $65.80

• What is the unit price for both stores?

CD SALE!!!!

5 for 49.95

HUGE SAVINGS!!! All discs on sale!

7 for $65.80

Dario has two options for buying boxes of pasta. At Corner Market he can buy seven boxes of pasta for $6. at Super Foods he can buy six boxes of pasta for $5.

At Corner Market he divided 7 by 6 and got 1.16666667. He then divided 6 by 7 and got 0.85714286. He was confused. What do these numbers tell you about the price of boxes of pasta at Corner Market?

Decide which makes more sense to you. Use that division strategy to compare the two store prices. Which store offers the better deal.

• Alison ran 24 miles in 3 hours. What is her average speed in miles per hour?

• Write 228 feet in 24 seconds as a unit rate in feet per second.

• Find the unit price per orange if it costs $2 for six oranges. Round to the nearest hundredth if necessary.

your turn: Find each unit rate. Round to the nearest hundredth.

• 300 tickets in 6 days

• 220 miles in 8 gallons

• $3 for 6 cans of soda

Choose the best buy

• The costs of different sizes of peanut butter are shown at the right. Which jar costs the least per ounce?

Size Price

12 oz $2.49

40 oz $5.30

80 oz $10.89

• At the Corner Market store, you can buy eight cans of tomatoes for $9. The cans are the same size as those at Canned Stuff, which sells six cans for $5. Are the tomatoes at Corner Market a better buy?

7-2 workbook problems

In book # 27 and 28

• SLOPE = rate

Exit pass

• Make up a comparison statement and swap with a partner. Choose the best buy.

Homework

• P 294: 1, 3, 10-23, 30, 31