What Are Follow-Through Marks and Why Do They Exist?
Imagine you make an arithmetic error in part (a) of a question and get the wrong answer. You then use that wrong answer correctly in part (b). Without follow-through marking, you would lose marks in both parts. With follow-through marking, you only lose the mark where the error occurred. Every subsequent part where you apply correct method using your wrong answer can still earn full marks. This rule exists because examiners are testing whether you understand the mathematical method, not whether you can perform arithmetic perfectly under pressure. If the method is correct, the understanding is there — and that is what the mark scheme rewards. Follow-through marking applies across all four major exam boards. CIE 0580 uses the notation ft explicitly in mark schemes. AQA 8300 and Edexcel 1MA1 use phrasing like their answer to (a) or follow through from part (a). OCR J560 uses similar language. In all cases, the principle is the same: correct method with a wrong input earns the mark.
How Follow-Through Works in Practice
The follow-through rule has three conditions that must all be met for the ft mark to be awarded. First, there must have been an error in a previous part that produced a wrong answer. Second, the student must use that wrong answer as their starting point in the current part. Third, the method applied to that wrong answer must be mathematically correct — the same method that would be used if the input were correct. CIE 0580 mark schemes use ft explicitly. A mark labelled A1ft means: the accuracy mark is awarded for the correct answer following through from the student's previous answer, even if that previous answer was wrong. AQA and Edexcel achieve the same effect by writing for their value from part (a) or by annotating marks with arrows showing the dependency chain. One crucial caveat: questions marked cao (correct answer only) do not allow follow-through. The CIE 0580 specification uses cao to flag questions where the answer must be exactly right, with no partial credit from follow-through. These are typically questions where a wrong input would make the subsequent method trivially simple or meaningless.
Worked Example 1 — Two-Part Percentage Question
Question: (a) Calculate 15% of £240. [2 marks] (b) The price is reduced by your answer to part (a). What is the new price? [2 marks] Correct answer to (a): 15% of £240 = 0.15 × £240 = £36. New price = £240 − £36 = £204. Student error: In part (a), the student calculates 15% of £240 as £30. They then write for part (b): New price = £240 − £30 = £210. Mark scheme: (a) M1 for a correct method such as multiplying by 0.15. A0 because £30 is incorrect. The student earns 1 out of 2. (b) M1ft for the correct method of subtracting their part (a) answer from £240. A1ft for £210, which is correct given their wrong input of £30. The student earns 2 out of 2 for part (b). Total: 3 out of 4 marks, despite the error in part (a). Without follow-through, this student would have scored 1 out of 4. Notice what made this work: the student clearly labelled their working, making it obvious to the examiner that they used their part (a) answer. If they had jumped straight to £210 with no working shown, the examiner could not confirm the method, and the ft marks might not have been awarded.
Worked Example 2 — Pythagoras into Trigonometry
Question: Triangle ABC has a right angle at B. AB = 5 cm, BC = 12 cm. (a) Calculate the length of AC. [2 marks] (b) Calculate angle BAC. Give your answer to 1 decimal place. [3 marks] Correct answers: (a) AC = √(25 + 144) = √169 = 13 cm. (b) sin(BAC) = 12/13, angle BAC = 67.4°. Student error: In part (a), the student subtracts instead of adding: AC = √(144 − 25) = √119 ≈ 10.9 cm. This is a very common error: the Cambridge 0580 examiner report (Jun 2022) notes that many candidates subtracted instead of adding when finding the hypotenuse. For part (b), the student correctly applies trigonometry with their wrong value: sin(BAC) = 12 ÷ 10.9. This gives arcsin(1.101), which is impossible since sine cannot exceed 1. In this case the error has created a mathematically impossible situation, so the follow-through cannot apply in part (b). However, if the student had made a different error in part (a) — say, getting AC = 11 through a different mistake — then using 11 correctly in the trigonometry would earn M1 and A1ft for the resulting angle. The key is that the follow-through only applies when the method makes mathematical sense with the wrong input.
Worked Example 3 — nth Term of a Sequence
Question: A sequence begins 3, 7, 11, 15... (a) Find the nth term of this sequence. [2 marks] (b) Use your nth term formula to decide whether 83 is a term in the sequence. Show your reasoning. [2 marks] Correct answer: (a) nth term = 4n − 1. (b) Set 4n − 1 = 83: n = 21. Since n is a positive integer, 83 is the 21st term. Student error: The student correctly identifies the common difference as 4 but writes nth term = 4n + 1 (sign error). For part (b), they write: 4n + 1 = 83, so 4n = 82, n = 20.5. Since n is not an integer, 83 is not in the sequence. Mark scheme: (a) M1 for identifying the first difference as 4. A0 for 4n + 1. 1 out of 2. (b) M1ft for the correct method of setting their formula equal to 83 and solving. A1ft for correctly concluding from their equation that n = 20.5 is not an integer and therefore 83 is not in their sequence. 2 out of 2. Total: 3 out of 4. The student's real-world conclusion is wrong (83 is in the sequence), but their method is correct given their starting formula, and the marks are awarded for the method.
When Follow-Through Does NOT Apply
Follow-through marking is not automatic on every question. There are situations where it does not apply, and recognising them prevents students from expecting ft marks that will not be awarded.
- cao questions (Correct Answer Only): CIE 0580 explicitly marks certain questions with cao to indicate that only the exact correct answer earns the mark. No follow-through is allowed. These typically involve probability (which must be between 0 and 1), integer answers, or final answers where the board requires precision.
- Show that questions: When the question tells you the answer, you must reach that specific value. There is no follow-through because the target is given. If you start with a wrong intermediate value and reach a different answer, you have not shown what was asked.
- Trivially simple follow-on: If an error in part (a) makes the method in part (b) trivially simple — for example, if a wrong value eliminates a variable entirely — the mark scheme may not award the ft mark because the difficulty has been removed.
- Mathematically impossible follow-on: As shown in Worked Example 2, if a wrong answer creates an impossible mathematical situation in the next part, the follow-through cannot apply.
Key Takeaways: Never Leave a Multi-Part Question Blank
The follow-through rule changes the strategic calculus of every multi-part exam question. Even if part (a) goes wrong, attempting every subsequent part using your wrong answer is almost always worthwhile. The examiner is looking for evidence of correct mathematical method. If that method is visible, the marks follow. Three practical rules: First, always attempt every part of a multi-part question, even if a previous part went badly. Second, write down your part (a) answer clearly and label your working in subsequent parts so the examiner can see you are using it. Third, show full method in every part — not just the final answer — so the method mark is available even if your specific arithmetic is slightly off. For more detail on how working earns marks, see our guide on method marks. For the specific rules about what written working the examiner expects, see our guide on showing your working.