Percentages
Percentages link directly to fractions and decimals and are tested extensively across Cambridge IGCSE papers. Questions range from simple percentage-of-an-amount calculations to reverse percentages and repeated percentage change problems.
What You'll Learn
- Calculating a percentage of an amount
- Increasing and decreasing by a given percentage
- Finding percentage change (profit, loss, interest)
- Working with reverse percentages
- Converting between percentages, fractions and decimals
Watch Out For These Mistakes
Students make these errors again and again. Knowing them in advance gives you a head start.
Dividing by the final amount instead of the original in reverse percentage questions
Confusing percentage increase with the new total amount
Using additive rather than multiplicative methods for repeated percentage change
What Examiners Say About Percentages
Insights pulled from Cambridge IGCSE (0580) examiner reports — the exact mistakes candidates make every year.
- Misconception●●●●●
For time intervals crossing midnight, split into two parts: time until midnight + time after midnight. Remember an hour has 60 minutes, not 100.
Source: CIE 0580 · Feb/March 2024 · Paper 1 · Q5
- Common Mistake●●●●●
For compound interest, the rate and the number of periods must MATCH. 0.25% per month over 5 years = 60 monthly periods (not 5). Don't silently convert to annual — apply the rate as given.
Source: CIE 0580 · Feb/March 2023 · Paper 4 · Q1a(iii)
- Common Mistake●●●●●
When finding bounds, always give the final answer in the SAME UNITS as the variable in the question. If l is in metres, bounds must be in metres — convert at the end if your working was in cm.
Source: CIE 0580 · May/June 2023 · Paper 1 · Q18
Based on 3of 500+ insights extracted from CIE 0580 examiner reports (2018–2024).
Exam Coverage
This topic appears in the Cambridge IGCSE past papers. Our AI tutor can help with it on any question.
Useful for this topic:
Related Topics
Fractions
Fractions form the backbone of Cambridge IGCSE maths, appearing in nearly every paper. Students must be confident adding, subtracting, multiplying and dividing fractions, as well as converting between improper fractions and mixed numbers.
Decimals
Decimal arithmetic is essential for real-world problem solving and calculator-based exam questions. Students need fluency with the four operations on decimals, place value understanding, and converting between decimals and other number forms.
Compound Interest
Compound interest builds on percentage multiplier methods to model growth and decay over time. Students apply repeated percentage change to financial contexts, population growth, and depreciation problems.
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Key number facts, rules, and formulae at a glance