Ratios

Ratio?

Ratio is a way of comparing two or more quantities

Examples:

◦Number of oranges to apples

◦Number of girls in a class compared to boys

There are 3 ways to express ratios:

As a fraction - ¾Using a colon - 3:4Using the word “to” - 3 to 4

What is the ratio of cats to mice?

Number of Cats: 3

Number of Mice: 6

Express the ratio as a fraction:

Express the ratio in words:

Express the ratio with a colon:

3 to 6

3:6

63

Team Wins Losses

S.D. Padres 16 11

L.A. Dodgers 18 13

Chicago Cubs 17 14

2001 Spring Training

List the wins to losses by the Cubs : 17 to 14

Wins to games played by the Cubs: 17 to 31

List the losses to wins by the Padres: 11/16

Losses to games played by the Padres : 11/27

Team Wins Losses

S.D. Padres 16 11

L.A. Dodgers 18 13

Chicago Cubs 17 14

2001 Spring Training

List the Dodgers wins to total games: 18 : 31

List the Dodgers losses to wins: 13 : 18

RED & BLUE Smarties

6 BLUE 3 RED

“The Ratio of BLUE to RED Smarties is 6 to 3

Blue : Red

6 : 3

Which symplifies to 2 : 1

“The Ratio of BLUE to RED Smarties is 6

Ratio Example Problems

…. Or… We can compare Red to Blue Smarties!

RED & BLUE Smarties

6 BLUE 3 RED

“The Ratio of RED to BLUE Smarties is 3 to 6”

Red : Blue

3 : 6

1 : 2

“The Ratio of RED to BLUE Smarties is 1:2”

“For every RED Smartie, there are 2 BLUES”

Simplifying Ratios

In the Smarties example, we changed 6:3 to 2:1

This is called Simplifying a ratio

We did it by dividing each number by 3

3 was the largest common factor

Try to simplify these

8:218:34:85:255:2

4:16:11:21:55:2 !!

Practice With Equivalent Ratios

Find an equivalent ratio by simplifying:

9030

Divide by 3031

= # 1

# 2 1215

45

= Divide by 3

# 3300125

125

= Divide by 25

30903030

÷÷

=

312315

÷÷

=

2530025125

÷÷

=

Equivalent ratios make

the same comparison.

Practice With Equivalent Ratios

Fill in the blank to make an equivalent ratio:

4

10 Multiply by 5

5 4

5 10

x

x # 4

# 5

# 6

20

50

3

7

10 3

10 7 x

x

30

70 Multiply by 10

20

12

2 20

2 12

10

6 Divide by 2

?

?

?

Sharing an amount in a given ratio“Bart and Maggie share a bag of 16 life savers with the ratio of 3:1”

This means “for every 3 life savers Bart gets, Maggie gets 1”4

Lifesavers for Maggie

12Lifesavers for Bart

Practice:Ratios worksheet