RatioRatio

Ratio?

• Ratio is a way of comparing two or more quantities

• E.g.– Number of Red Smarties in a box

compared to Blue– Number of girls in a class compared

to boys

For exampleRED & BLUE Smarties

6 BLUE 3 RED

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

Blue : Red

6 : 3

2 : 1

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

…. Or…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 !!

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

This means “for every 3 sweets Bart gets, Maggie gets 1”

4 12

… quicker way….“Bart and Maggie share a bag of 16 sweets in the ratio 3:1”

1 share 3 shares

Another way to think of this 3:1 is shares

Bart gets 3 shares to Maggie’s 1

So there are actually 4 shares 16 sweets shared by 4

16 ÷ 4 = 4 in a share

1 x 4 3 x 44 12