Maths Olympiad · topic 13 of 33 · free

Ratio and the unitary method — Maths Olympiad practice

The unitary method means “go through one”: find the cost of one pen, the size of one part of a ratio, or the work of one worker — then scale up. Watch out for inverse questions: more workers take fewer days.

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How to solve it

Go through one — “find the value of one thing (or one part), then multiply”

  1. Unitary: cost of one = total ÷ number; then multiply by how many you need.
  2. Ratio p : q of a total: one part = total ÷ (p + q); a share = its parts × one part.
  3. Workers and days go the opposite way: total work = workers × days; days = total work ÷ new number of workers.

Use it for: Prices, recipes, sharing in a ratio, and time-and-work questions in Class 5–8.

🧮 Check your own sums with the free Ratio calculator — it shows the working.

Worked example: 6 workers can build a wall in 10 days. How many days will 4 workers take, working at the same speed? 15 days

  1. Fewer workers take longer: total work = 6 × 10 = 60 worker-days.
  2. 60 ÷ 4 = 15.

Check: 4 workers × 15 days = 60 worker-days, the same as 6 × 10 ✓

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✓ Written and checked by the TalentJR team · Updated 13 Oct 2026 · How we make our lessons

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🖨️ Ratio and Unitary Method Worksheet for Olympiad

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