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Quantitative aptitude · lesson 9 of 30 · free

Percentage formula — Quantitative aptitude for kids

Percent means “out of 100”, so 35% is 35/100. Three formulas cover almost every question: x% of y, what percent one number is of another, and finding the whole when you know a part.

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The method

Out of 100 — “x% of y = x × y ÷ 100; percent = part ÷ whole × 100”

  1. x% of y = x × y ÷ 100.
  2. What percent is a of b? a ÷ b × 100.
  3. If x% of a number is A, the number is A × 100 ÷ x.
  4. A fraction to a percent: multiply by 100 (3/4 = 75%).

Use it for: Marks and results, discounts, interest, data interpretation and every Part 2 lesson.

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

Worked example: What percent of 80 is 28? → 35

  1. Percent = part ÷ whole × 100 = 28 ÷ 80 × 100.
  2. 28 × 100 ÷ 80 = 35.

Check: 35% of 80 = 35 × 80 ÷ 100 = 28 ✓

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

✏️ Practice

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

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🏁 Lesson 9 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 💯 Percent Pathfinder badge when you pass — and a certificate when you finish all 10 lessons of Part 1 · Number skills. You can still take the test without signing in.

🖨️ Percentage Worksheet

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