- 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%
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.
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)