Ratios and Proportions

Simplifying Ratios

Divide both values by their Greatest Common Divisor (GCD). 12:8 → GCD is 4 → 3:2. 100:75 → GCD is 25 → 4:3. A simplified ratio shows the same relationship with the smallest whole numbers.

Scaling Proportions

If paint is mixed at 2 parts blue to 3 parts white and you want 10 litres of blue, you need: 3/2 × 10 = 15 litres of white. The ratio stays the same; the quantities scale proportionally.

Common Uses

Cooking: scaling ingredients to a different number of servings. Cement mixing: 1 cement to 4 sand to 8 aggregate. Map scales: 1:25,000 means 1cm on map = 250m in reality. Scale models: 1:72 scale means the model is 72 times smaller than the original.

Ratio Calculator

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