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Check the numbers, signs, units and labels in the diagram. A small detail can change the answer.
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Match your result with the options shown on this website. If none of them is correct, the note below explains why.
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The notes below point out corrections and explain answers that need care. Click a question to read it with its solution. If you spot another mistake, please tell us the year, subject and question number through our contact page.
Question-wise notes
| Question | What to keep in mind |
|---|---|
| 2020 · Biology 6 | The change described in the answer is expected, but it does not necessarily mean that the whole ecosystem will collapse. |
| 2020 · Biology 11 | Extra text in the table has been removed. The cell types and their counts remain the same. |
| 2020 · Chemistry 1 | The solution uses the usual hexagonal-prism unit cell. |
| 2020 · Chemistry 15 | The answer shows the product expected from the reaction scheme. In practice, the nitro group would make preparation of the Grignard reagent difficult. |
| 2020 · Mathematics 5 | None of the given options satisfies the stated condition for real numbers. |
| 2020 · Mathematics 8 | The option should read 187. The extra equation attached to it was not part of the question. |
| 2020 · Physics 1 | For a finite maximum, B must be positive. The sign shown in the answer also assumes that A is positive. |
| 2020 · Physics 4 | The answer gives the largest allowed mass ratio. Other, smaller ratios may also allow equilibrium. |
| 2020 · Physics 5 | The quantity inside the inverse-sine function must be no greater than 1 for the answer to be valid. |
| 2020 · Physics 6 | The top resistor on the right is R. The circuit diagram has been corrected to show this. |
| 2020 · Physics 7 | The extra equation after option D has been removed. The answer gives the smallest angle for equilibrium; it does not mean that only one angle is possible. |
| 2020 · Physics 13 | The comparison assumes the same quantum efficiency for both colours, with both frequencies above the threshold frequency. |
| 2021 · Biology 5 | A population bottleneck can itself lead to genetic drift. Keep this in mind when comparing the two terms in the options. |
| 2021 · Mathematics 8 | The calculation gives 26, but 26 is missing from the four options. |
| 2022 · Biology 1 | The matching table has been corrected to follow the question paper. |
| 2022 · Biology 2 | Repeated numbers in one option have been removed to match the question paper. |
| 2022 · Biology 15 | X represents a distance. The marks around it should not be read as a derivative. |
| 2022 · Chemistry 1 | One of the options should contain O₂. It has been corrected. |
| 2022 · Chemistry 15 | The structure has a fluorine atom at each of the two para positions. The diagram has been corrected. |
| 2022 · Mathematics 5 | Use the growth rule given in the question. It is a mathematical model for this problem, not a description of how the climate actually changes. |
| 2022 · Mathematics 7 | The subscript should be n+1. In this question, the natural numbers start at 1. |
| 2022 · Physics 3 | When the full normal reaction is included, none of the options matches the exact result for the sliding bowl. Read the solution before marking this question. |
| 2022 · Physics 13 | The ray diagram and inequality have been corrected. This is Physics question 12 in the original paper and question 13 on this website. The image lies between the object and the lens; its exact distance cannot be found without more information about the refractive indices. |
| 2022 · Physics 15 | The flat parts of the graph show a simplified picture. At fixed power, the current need not stay constant as the frequency changes. |
| 2023 · Biology 4 | Metaphase is the expected answer. However, the wording “first affected” leaves room to consider prophase too; the solution explains the distinction. |
| 2023 · Biology 10 | C is the expected matching option, but the pairing of FSH with ovulation needs care. Read the explanation of the hormones involved. |
| 2023 · Chemistry 10 | The missing option has been added from the question paper. The earlier version repeated II and IV. |
| 2023 · Mathematics 1 | The given value is f(1). It should not be read as a derivative. |
| 2023 · Physics 10 | Both fixed charges are +q. The diagram has been corrected. |
| 2023 · Physics 14 | The angular momentum given is 2ℏ, where ℏ is the reduced Planck constant. |
| 2024 · Biology 8 | The missing words have been added to match the question paper. |
| 2024 · Biology 15 | Option B should say low hydrogen-ion concentration. This is different from low pH. |
| 2024 · Chemistry 4 | The formula is XeF₄. The earlier text contained a typing error. |
| 2024 · Chemistry 12 | Use Planck’s constant as 6.6 × 10⁻³⁴ J s. The solution also assumes that each absorbed photon releases one photoelectron. |
| 2024 · Mathematics 12 | The locus covers only the right-hand half of the parabola named in the answer. |
| 2024 · Mathematics 14 | The starting point is an endpoint approached along the curve. The derivative grows without bound there, so it cannot be treated as an ordinary point with a finite slope. |
| 2024 · Physics 3 | The two masses are M and M/2. An extra mark on M has been removed. |
| 2024 · Physics 6 | The solution is for small oscillations. It neglects fluid inertia and drag. |
| 2024 · Physics 8 | A typing error has been corrected. The physical data in the question are unchanged. |
| 2024 · Physics 11 | A typing error has been corrected. The physical data in the question are unchanged. |
| 2024 · Physics 12 | A typing error has been corrected. The physical data in the question are unchanged. |
| 2024 · Physics 13 | The missing word and the way the numbers are written have been corrected to match the question paper. |
| 2024 · Physics 14 | A typing error has been corrected. The physical data in the question are unchanged. |
| 2025 · Biology 8 | One option had been split into two parts. It has been joined back together as in the question paper. |
| 2025 · Chemistry 13 | One option should read 0.24 fs; the decimal point was missing. Use the option letters shown on this website when checking your answer. |
| 2025 · Physics 11 | The solution uses the slow change described in the question, so the adiabatic approximation applies to the motion. |
| 2025 · Physics 15 | The expected answer depends on the starting condition. Read the opening part of the solution before using the result. |
| 2026 · Physics 7 | The expected answer assumes that the upward electric force is weak. A stronger force would need a different case to be considered. |
| 2026 · Physics 11 | The solution uses an ideal solenoid model in which magnetic flux is conserved. Read the note in the solution about this assumption. |
| 2026 · Physics 13 | The usual nonrelativistic calculation gives the expected result. At the very short wavelength stated, however, this approximation needs care; see the explanation in the solution. |
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