This study notes covers Common Percentage Traps within Percentage Problems for GCSE Mathematics. Revise Percentage Problems in Number for GCSE Mathematics with 14 exam-style questions and 22 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 8 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.
Common Percentage Traps
- Adding VAT to VAT: Don't add 20% VAT to a price that already includes VAT
- Double Discounts: 20% off then 10% off ≠ 30% off (it's actually 28% off)
- Percentage vs Percentage Points: Interest rising from 3% to 5% is a 2 percentage point increase, not 2%
- Base Confusion: Make sure you know what the percentage is OF
- Reverse Calculation Errors: To remove 20% VAT, divide by 1.2, don't subtract 20%
Practice questions for Percentage Problems
What is the multiplier for a 30% increase?
Work out 20% of 60.
Quick recall flashcards
A £60 item has 25% off. What do you pay?
Method 1: Discount = £60 × 0.25 = £15, Pay = £60 - £15 = £45
Method 2: Pay = £60 × 0.75 = £45
Answer: £45
What is the formula for simple interest?
I = PRT/100
where P = Principal, R = Rate (%), T = Time (years)