5.2 Unit Rates Lesson - kutz

A rate is a ratio that compares two different kinds of

quantities.

2 teachers for 24 students:
2 teachers
24 students
=
12
teacher
students
15 strike-outs in 9 innings
15 strike-outs
9 innnings
=
strike-outs
innings
When you have a unit rate, the second quantity is 1.
Example 240 miles in 4 hours.
240 miles
4 hours
÷
4
4
=
miles
hour

Suppose you drove to San Francisco in 3 hours.

What would be the unit rate?

don't forget the unit - mph
96 miles ÷  3 hours =

An easier way is to simply divide the

distance by the time.

( miles per hour )

We use unit rates all the time. Many people are

paid by the hour.

Suppose you work at a coffee shop and make

$9.50 an hour and work 8 hours.

How much would you make?

$9.50 x 8 hours = $76.00

Suppose you stayed late and worked 10 hours?
$9.50 x

your answer is money so it needs 2 decimals places and a $ sign 

=  
example - $75.00

An ice cream cone may be 35 calories per ounce.

If the ice cream cone is 7 ounces, how many

calories are in the ice cream cone.

Suppose a different cone was 45 calories/ounce.

How many calories would be in the whole cone?

35  calories/oz.  x  7 ounces = 245 calories

calories/oz.  x

don't forget the unit - calories
oz.  =
Unit rates can be used to find the better buy.
$1.20  ÷ 16  =  $

A)     12 ounce can of soda for $.84

B)     16 ounce bottle for $1.20
$0.84 ÷ 12 =  $
What's the better deal?
/ oz.
/ oz.

16 oz. bottle

12 oz. can

What's the better buy?
A)  4 oz.  Snickers Bar for $0.80
B)  6 oz.   3 Musketeers Bar for  $0.90

3 Musketeers

Snickers

There are 350 students in 11 classes. About how

many students are in each class?

Sometimes you just want to estimate the unit rate.

Use compatible numbers.

350 ÷ 10 would be

So what would be the best guess ( estimate )?

350 students per class

10 students per class

32 students per class

39 students per class

students per class

There are 123 students in 6 classes. About how

many students are in each class?

Sometimes you just want to estimate the unit rate.

Use compatible numbers.

120 ÷ 6 would be

So what would be the best guess ( estimate )?

 15 students per class

18 students per class

 21 students per class

 6 students per class

students per class
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