Simple Ratio

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Find unknown values when two quantities are in a given ratio.

Ratio problems express a relationship between two quantities. If A:B = 2:3 and you know A=10, you can find B by first finding the multiplier (10÷2=5) and then applying it to the other part (3×5=15). The ratio tells you the relative sizes, and the multiplier scales it to actual values.

If A:B = m:n and A = x, then B = x × (n/m)

• If A:B = 2:3 and A = 10, then B = 10 × (3/2) = 15
• If X:Y = 3:4 and Y = 20, then X = 20 × (3/4) = 15
• If P:Q = 5:2 and P = 35, then Q = 35 × (2/5) = 14

How to recognize it

• Two quantities described as 'in the ratio' of X:Y
• One value is given, the other is unknown
• Find the multiplier by dividing the known value by its ratio part

Common mistakes

• Dividing by the wrong ratio part
• Confusing which value corresponds to which part of the ratio
• Adding/subtracting instead of multiplying

Practice guidance

Numerical Reasoning