7th Grade Math

268 Proportions and Similarity

Examples 1 and 2 Find each unit rate. Round to the nearest hundredth if necessary.

1. 90 miles on 15 gallons 2. 1,680 kilobytes in 4 minutes
   33 5 pounds for $2.49 4. 152 feet in 16 seconds

Example 3 5. CDS Four stores offer customers bulk Bulk CD Offers

Store Offer

CD Express 4 CDs for $60

Music Place 6 CDs for $75

CD Rack 5 CDs for $70

Music Shop 3 CDs for $40

CD rates. Which store offers the

best buy?

Example 4 6. TRAVEL After 3.5 hours, Pasha had

traveled 217 miles. If she travels at a

constant speed, how far will she have

traveled after 4 hours?

Use a Unit Rate

FACE PAINTING Lexi painted 3 faces in 12 minutes at the

Crafts Fair. At this rate, how many faces can she paint in

40 minutes?

Method 2 Find a Unit Rate

Find the unit rate. Then multiply this unit rate by 40 to find the

number of faces she can paint in 40 minutes.

3 faces in 12 minutes = _12 min 3 faces ÷÷ 1212 = _0.25 faces1 min Find the unit rate.

_0.25 faces

1 min

· 40 min = 10 faces Divide out the common units.

Method 1 Draw a Bar Diagram

12 min

4 min

time to paint

one face

time to paint

one face

time to paint

one face

4 min 4 min

It takes 4 minutes to paint one face. In 40 minutes, Lexi can paint

40 ÷ 4 or 10 faces.

Using either method, Lexi can paint 10 faces in 40 minutes.

e. SCHOOL SUPPLIES Kimbel bought 4 notebooks for $6.32. At this

same unit price, how much would he pay for 5 notebooks?

Real-World Link

Face paint can be

made from 1 teaspoon

cornstarch and

_^12 teaspoon each of

water and cold cream.

RRR

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