GCSE Maths Practice: percentages

Question 4 of 10

This quiz question helps you practise finding a simple percentage of a number — an essential GCSE Maths skill used in discounts, grades, and interest calculations.

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\( \textbf{What is } 10\% \textbf{ of } 150? \)

Choose one option:

Estimate first: 10% is one-tenth. Divide the number by 10 to check if your final answer seems reasonable.

Understanding Percentages

Percentages represent parts of a whole. The word comes from the Latin 'per centum', meaning 'by the hundred'. They are used everywhere — from exam results to discounts and bank interest rates. In GCSE Maths, learning how to calculate percentages accurately is essential for success in both exams and real life.

Concept Explained

To find a percentage of a number, multiply the number by the percentage and then divide by 100. The formula is:

Percentage of a number = (Percentage × Number) ÷ 100

For example, to find 25% of 80, multiply 80 × 25, then divide by 100. The result is 20.

Step-by-Step Method

  1. Convert the percentage to a fraction or decimal. For instance, 10% = 10/100 = 0.1.
  2. Multiply this value by the given number.
  3. Check that your answer makes sense — if the percentage is small, the answer should also be smaller than the original number.

Worked Examples

  • Example 1: 20% of 150 = (20/100) × 150 = 30.
  • Example 2: 5% of 60 = (5/100) × 60 = 3.
  • Example 3: 15% of 200 = (15/100) × 200 = 30.

Common Mistakes to Avoid

  • Multiplying by the percentage without dividing by 100 — this makes your answer ten times too large.
  • Rounding numbers too early; it’s better to round only at the end.
  • Confusing 'percentage of' and 'percentage increase' — they are different operations.

Real-Life Applications

Percentages are used in nearly every area of life. In shops, you might see '20% off' signs — meaning you pay 80% of the original price. In banking, you earn or pay interest based on a percentage. In exams, your score is often given as a percentage of the total marks. Being confident with these calculations can save you money and help you make better decisions.

Quick Mental Maths Tip

To find 10% of any number, simply divide it by 10. To find 5%, halve the result of 10%. For example, 10% of 90 is 9, and 5% is half of that, 4.5. These shortcuts make estimation faster and reduce calculator use.

Frequently Asked Questions

Q1: How do I find 1% of a number?
Divide the number by 100. For example, 1% of 400 is 4.

Q2: How can I increase a number by a percentage?
Add the percentage to 100% and multiply. For example, to increase 200 by 15%, multiply by 1.15 to get 230.

Q3: How do I decrease a number by a percentage?
Subtract the percentage from 100% and multiply. For a 20% decrease on 150, multiply by 0.8 to get 120.

Summary

Understanding percentages means understanding proportional thinking. Always multiply by the percentage and divide by 100, or use mental shortcuts for simple cases. Check your answer by estimating — for example, if you are finding 10%, the answer should be roughly one-tenth of the original number. Practising a variety of examples helps build confidence for GCSE Maths exams and real-world applications like finance, data interpretation, and sales.