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Maths Olympiad · topic 16 of 33 · free

Simple interest — Maths Olympiad practice

Simple interest is the same amount every year: R per cent of the money you started with. Multiply principal, rate and time, divide by 100. Turn the formula round to find the rate or the time.

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How to solve it

P × R × T ÷ 100 — “interest grows by the same amount every year”

  1. Simple interest = P × R × T ÷ 100 (P = principal, R = rate % per year, T = years).
  2. Amount = principal + interest.
  3. Rate = SI × 100 ÷ (P × T); time = SI × 100 ÷ (P × R).

Use it for: Bank deposits, loans and every interest question in Class 7–10.

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

Worked example: What is the simple interest on ₹5000 at 8% per year for 3 years? ₹1200

  1. SI = 5000 × 8 × 3 ÷ 100.
  2. 5000 × 8 × 3 = 120000, and ÷ 100 gives ₹1200.

Check: One year’s interest is 8% of ₹5000 = ₹400, and 3 × ₹400 = ₹1200 ✓

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

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🖨️ Simple Interest Worksheet for Maths Olympiad

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