Ratio & Proportion

Ratio and proportion are ways of comparing quantities. These topics appear frequently in the GL 11+ exam, often in word problems that test your ability to share amounts fairly, scale recipes, or work with maps and models.

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What Is a Ratio?

A ratio compares two or more quantities using the symbol :

If there are 3 red sweets and 5 blue sweets, the ratio of red to blue is 3 : 5.

Key Points

• The order matters: 3 : 5 is different from 5 : 3.
• A ratio does not tell you the actual amounts — only the relationship between them.
• Ratios can have more than two parts: red : blue : green = 2 : 5 : 3.

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Simplifying Ratios

Simplify a ratio by dividing all parts by their Highest Common Factor (HCF).

Simplify 12 : 18

• HCF of 12 and 18 = 6
• 12 ÷ 6 : 18 ÷ 6 = 2 : 3

Simplify 15 : 25 : 10