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NumberExam Tips

Common Mistakes to Avoid

Part of Percentages · GCSE GCSE Mathematics revision

This exam tips covers Common Mistakes to Avoid within Percentages for GCSE Mathematics. Revise Percentages in Number for GCSE Mathematics with 14 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 14 of 16 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.

Topic position

Section 14 of 16

Practice

14 questions

Recall

22 flashcards

Common Mistakes to Avoid

❌ Wrong: 30% of 80 = 30 × 80 = 2400 ✅ Right: 30% of 80 = 0.3 × 80 = 24

Convert percentage to decimal first

❌ Wrong: 20% increase = × 0.2 ✅ Right: 20% increase = × 1.2

Add to 100% for increase (120% = 1.2)

❌ Wrong: 15% decrease = × 1.15 ✅ Right: 15% decrease = × 0.85

Subtract from 100% for decrease (85% = 0.85)

Keep building this topic

Read this section alongside the surrounding pages in Percentages. That gives you the full topic sequence instead of a single isolated revision point.

Higher Level: Percentage Points vs Percentage ChangeExam TipsParts per HundredWhat Are Percentages?

Practice Questions for Percentages

Which calculation correctly finds 35% of £240 using the decimal method?

  • A. 240 ÷ 35
  • B. 240 × 3.5
  • C. 240 × 0.35
  • D. 35 ÷ 240
1 markfoundation

Which formula correctly expresses one quantity as a percentage of another?

  • A. (part ÷ whole) × 100
  • B. (whole ÷ part) × 100
  • C. (part × whole) ÷ 100
  • D. (whole − part) × 100
1 markfoundation

Quick Recall Flashcards

Percentage to decimal
Divide by 100 75% = 0.75 8% = 0.08 150% = 1.5 Move decimal point 2 places left
What is a percentage?
Parts per hundred Percent = per cent = per 100 % symbol means 'out of 100' 50% = 50/100 = half

14 questions on Percentages — practise free

Instant marking, adaptive difficulty, and 22 spaced repetition flashcards. Free until your GCSEs.

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