Simple interest and the rate — How to calculate percentage

How to work it out

P × R × T over 100 — “interest = money kept × rate × years ÷ 100”

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

Use it for: Savings accounts, fixed deposits, loans and the Class 7–8 simple interest chapters.

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

Worked example: ₹2000 earns ₹480 simple interest in 3 years. What is the rate of interest per year, in percent? → 8

✏️ Practice

Work it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.

🏁 Lesson 19 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.

🏅 Sign in with Google to earn the 🏦 Interest Ace badge when you pass — and a certificate when you finish all 6 lessons of Part 4 · Percentages and money. You can still take the test without signing in.

🖨️ Simple Interest Rate Worksheet

• Worksheet set 1 (PDF)
• Worksheet set 2 (PDF)
• Worksheet set 3 (PDF)