Sheet № 76 · Foundation + Higher · AQA · Edexcel · OCR
Percentage of an Amount –
Finding a percentage of an amount is one of the most useful skills in GCSE Maths and in everyday life. From calculating discounts to working out VAT, this topic appears on both calculator and non-calculator papers across AQA, Edexcel, and OCR.
§Key definitions
Question:
Find 35% of 240 without a calculator.
Answer:
162 boys play football
Q1 (Foundation):
Find 15% of 360 without a calculator.
Q2 (Foundation):
Find 12.5% of 480.
Q3 (Higher):
A car is worth £18,500. Its value decreases by 8.5%. What is the new value?
§Formulas to memorise
Percentage of an amount = (percentage / 100) × amount
Multiplier method: percentage of amount = decimal multiplier × amount, where the multiplier = percentage ÷ 100
10% of a number = the number ÷ 10
Non-calculator approach: — Find 10% by dividing by 10. From there, find 5% (halve the 10%), 1% (divide the original by 100), and build up to the required percentage.
Calculator/multiplier approach: — Divide the percentage by 100 to get a decimal. Multiply the amount by this decimal.
Worked example
Find 35% of 240 without a calculator.
Working:
⚠ Common mistakes
- ✗Moving the decimal point the wrong way. When finding 10%, divide by 10 (move the decimal one place left), not multiply. Students sometimes multiply by 10 instead.
- ✗Forgetting to add the percentage back on. If a question asks for the total cost after adding VAT, you must add the VAT amount to the original price — do not give just the VAT amount.
- ✗Using the wrong multiplier. 15% as a decimal is 0.15, not 1.5 or 0.015. Always divide the percentage by 100 carefully.
✦ Exam tips
- →On non-calculator papers, show the 10% and 1% building blocks clearly. Examiners award method marks for these intermediate steps.
- →On calculator papers, writing the multiplier calculation (e.g. 0.35 × 240) earns a method mark even if you press the wrong button.
- →Read the question carefully — does it ask for the percentage amount only, or the new total?