# Ratio

"A ratio is a comparison between two like quantities in the same units."

Simplest form ratios

A ratio, such as a:b can be reduced similarly like fractions, using a lowest common denominator approach.

Eg.

2:4 is the same as

1:2

The example ratios 2:4 and 1:2 are also known as equivalent ratios because they really are the same. See also Proportion.

Finding a ratio between quantities

change into same units, then

put lower one on the left

find the simplest

Eg.

300mls and 1.5litres goes to

300mls and 1500 litres

300:1500

3:15

1:5

Dividing a quantity into ratios

If you are given a ratio and a total, you can work out the ratio amounts thus:

Add the parts

Divide the total by the parts to find 1 part

Times the ratio amount by 1 part.

Eg.

20m total, 2:3

2+3=5

20/5=4

4*2 is 8:4*3 is 12

8 metres, 12 metres.

If you are given a ratio and one part:

Divide value by the ratio amount, gives you multiplying factor

Times factor by other ratio amount, now you know value of both sides

add them together for total.

Eg.

5:7, 5 parts is 20

20/5 is 4

7 times 4 is 28

28 + 20 is 48 total

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