Ratio
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 example
RED & BLUE Smarties
Blue : Red
6:3
2:1
6 BLUE
3 RED
“The Ratio of BLUE to RED Smarties is 2:1”
6 to 3”
…. Or…
RED & BLUE Smarties
Red : Blue
3:6
“For every RED Smartie, there are 2 BLUES”
1:2
6 BLUE
3 RED
“The Ratio of RED to BLUE Smarties is 1:2”
3 to 6”
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
8:2
18:3
4:8
5:25
5:2
4:1
6:1
1:2
1:5
5:2 !!
Sharing an amount in a given ratio
“Bart and Maggie share a bag of 16 sweets in the ratio 3:1”
4
This means
“for every 3
sweets Bart
gets, Maggie
gets 1”
12
“Bart and Maggie share a bag of 16 sweets in the ratio 3:1”
… quicker way….
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
1x
share
44
3x
shares
12
4