Warm-up:1. Solve: 3x – 4 – 5x < 102. Simplify:

A) -3 (x – 5)B) 2 (3x – 4)

18December 15, 2010

HW: pg. 295 #21-30

Objective: SWBAT use unit rates to solve real world problems.

Unit Rates

Definitions*Write this down!

• Rate – ratio that compares 2 quantities measured in different units

• UNIT rate – rate for 1 unit (denominator of 1)

What are some RATES in the real world?

• Driving miles per hour• Typing words per

minute• Cost per bottle• Cost per ounce• Heartbeats per minute• Reading pages per hour• Miles per gallon

Scenario 1: Ms. Han’s gas mileage

• HIGHWAY (road trip to Philly and Virginia) I drove 386.8 miles and pumped 10.694

gallons. How many miles per gallon did I get? 386.8 miles = miles10.694 gallons 1 gallon

36.17

36.17 miles per gallon

• CITY (back and forth to work) I drove 300.12 miles and pumped 10.612

gallons. How many miles per gallon did I get? 300.12 miles = miles

10.612 gallons 1 gallon

28.28

28.28 miles per gallon

Scenario 1: Ms. Han’s gas mileage

Scenario 2: Road trip miles per hour

• On my road trip to Philly, it took me 2 hours to drive 120 miles to get there.

• How fast did I drive?120 miles = miles 2 hours 1 hour

60

60 mph

• On my way home, I drove the same 120 miles but in 1 hour and 45 minutes.

• How fast did I drive?120 miles = miles

1.75 hours 1 hour

68.57

68.57 mph

Scenario 2: Road trip miles per hour

Scenario #3: Grocery shopping

• Sometimes sale prices are deceiving.• You have to check the UNIT PRICE! (the little

orange sticker)• You can use unit rates to figure out the better

buy.• Divide: COST ÷ UNIT (to get the price per unit)• Ex. $12 for 6 hamburgers – how much was 1

hamburger? • $12 ÷ 6 burgers = $2 per burger

Which is the better buy?

• 2 liters of milk at $3.80• 1.5 liters of milk at $2.70

• 10 pencils for $4.00 at Staples• 6 pencils for $2.70 at Office Depot

• Kellogg’s Fruit Loops 12.2 oz box for $4.58• Giant Brand Fruit Loops 28 oz box for $4.49

Coffee – which is the best buy?

• Starbucks: 14 oz for $11.19• Dunkin Donuts: 26 oz for $7.99• Don Francisco: 12 oz for $6.25• Folgers: 3.95 oz for $5.79

Your turn!

• Worksheet – compare Giant versus Sam’s Club