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Fractions form the backbone of GCSE 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.
Students make these errors again and again. Knowing them in advance gives you a head start.
Adding numerators and denominators separately without finding a common denominator
Forgetting to flip the second fraction when dividing (multiply by the reciprocal)
Not simplifying the final answer to its lowest terms
Insights pulled from Cambridge IGCSE (0580) examiner reports — the exact mistakes candidates make every year.
For time intervals crossing midnight, split into two parts: time until midnight + time after midnight. Remember an hour has 60 minutes, not 100.
“16 h 32 min from subtracting the times was just one of many incorrect responses seen, some of which suggested there is 100 minutes in an hour! Clearly working out time periods is something that many simply guess at rather than making a structured response to periods of time going over the end of one day.”
Source: CIE 0580 · June 2024 · Paper 1 · Q5
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.
“Fewer fully correct responses were seen as a number of candidates struggled to deal correctly with a compound interest rate of 0.25% per month. Many treated 0.25% per month as 3% per year and 350(1 + 3/100)^5 was frequently seen. Some appeared not to notice that the interest was monthly, instead treating it as annual interest.”
Source: CIE 0580 · June 2023 · Paper 4 · Q1a(iii)
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.
“This area of the syllabus is often found to be challenging for many candidates. Also the length of piece of wood, l, was given in metres but the extra information to find the limits was given in centimetres. The answer line used l, so the limits were expected to be in metres not centimetres.”
Source: CIE 0580 · November 2023 · Paper 1 · Q18
Based on 3of 510+ insights extracted from CIE 0580 examiner reports (2018–2024).
This topic is tested by the following exam boards. Our AI tutor covers each one with board-specific content.
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.
Percentages link directly to fractions and decimals and are tested extensively across all exam boards. Questions range from simple percentage-of-an-amount calculations to reverse percentages and repeated percentage change problems at higher tier.
Algebraic fractions combine fraction skills with algebraic manipulation and are tested at higher tier. Students must simplify, add, subtract, multiply and divide fractions that contain variables, often needing to factorise first.
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