Ratio and Proportion

Ratio and proportion are about comparing quantities and describing how they relate to each other. You use them when following a recipe, reading a map, or working out fair shares. This topic is introduced in Year 6.

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What is a Ratio?

A ratio compares two or more quantities of the same type.

If a bag contains 3 red sweets and 5 blue sweets, the ratio of red to blue is 3:5 (read as "3 to 5").

The order matters — 3:5 is not the same as 5:3.

Writing ratios:

• For every 3 red sweets there are 5 blue sweets.
• The total number of parts is 3 + 5 = 8.
• Red sweets make up 3/8 of the bag; blue sweets make up 5/8.

Part-to-Part and Part-to-Whole

This is a very common source of confusion. Make sure you know which type of comparison is being asked for.

Part-to-part ratio compares one part with another part.

• 3 red and 5 blue → red to blue = 3 : 5

Part-to-whole compares one part with the total.

• 3 red out of 8 total → red is 3/8 of the bag.