Maths marks come in two kinds: method marks for doing the right thing, and accuracy marks for getting the right number. A wrong answer with clear, correct working can still score most of the marks. A right answer with no working can, on some questions, score none. Showing working is not politeness — it is where the marks live.
What examiners are actually looking for
A mark scheme for a multi-mark maths question is a list of things that must appear on the page. Typically it reads something like: one mark for a correct method for finding the area, one mark for correctly substituting into the formula, one mark for the correct final answer with units. Each line is awarded independently.
That independence is the whole game. If you substitute correctly but slip on the arithmetic, you lose the accuracy mark and keep the method marks. If you do it all in your head and write "42" on the answer line, there is nothing for the examiner to award except the final mark — and if 42 is wrong, the page is worth zero.
There is also a rule that works in your favour called "follow through". If you make an error early and then use your wrong value correctly for the rest of the question, later marks can still be awarded — but only if the examiner can see that you used it correctly. No working, no follow-through.
What good working looks like
Step 1 — Write down what you are finding. A short label costs three seconds: "Area of triangle =", "Speed =", "Let x = number of red counters". It orients the examiner and it orients you.
Step 2 — Write the formula or rule before the numbers. Area = ½ × b × h on its own line, then the substitution underneath. Many mark schemes award a mark for the correct formula alone.
Step 3 — Substitute in full before you simplify. ½ × 8 × 5 deserves its own line. Do not jump straight to 20.
Step 4 — One operation per line, going down the page. Not across. A line of maths that snakes sideways with equals signs joining unequal things is where marks disappear.
Step 5 — State the answer with units. On its own line, on the answer line if there is one, with cm², m/s, £ or degrees as appropriate. Units are frequently a mark in their own right.
Step 6 — Say what the answer means if the question asked a question in words. "So the cheaper option is Shop B, by £3.40." A question that ends "which is better value? Give a reason" is not answered by a number.
The worked example, side by side
Question: A rectangle has a perimeter of 34 cm. Its length is 4 cm more than its width. Find its area. (4 marks)
Weak response
w = 6.5
l = 10.5
68.25 cm²
Correct answer, and it will score full marks — but only because it happens to be right. Had the student slipped anywhere, there is nothing to rescue.
Strong response
Let width = w, so length = w + 4
Perimeter: 2(w) + 2(w + 4) = 34
4w + 8 = 34
4w = 26
w = 6.5 cm
Length = 6.5 + 4 = 10.5 cm
Area = 6.5 × 10.5
Area = 68.25 cm²
Every mark-scheme line is visible: the setup, the equation, the solve, the area with units. If the student had mis-typed 6.5 × 10.5 into the calculator and written 65.25, three of the four marks would still be safe.
Where students lose marks most often
| Habit | What it costs |
|---|---|
| Doing several steps mentally | All method marks if the answer is wrong |
| Rubbing out working that "looks messy" | Marks that were already earned |
| Rounding early, then using the rounded value | Accuracy marks throughout the rest of the question |
| Writing answers with no units | The units mark, on nearly every measure question |
| Using = to join things that are not equal | Method marks, and sometimes the examiner's patience |
| Working in the margin, answer in the box | Follow-through marks, because the two are not linked |
The rubbing-out one is worth dwelling on. If you decide your first attempt is wrong, put a single neat line through it and carry on below. Crossed-out work is still marked if nothing else is offered, and it costs nothing to leave it. Erased work is gone.
"Give a reason" and "you must show your working"
Two phrases in a question change what is required.
"You must show your working" means unsupported answers score zero, full stop. This appears on questions where the answer could be guessed or found on a calculator, and it is not a suggestion.
"Give a reason for your answer" or "Justify" means a sentence is required, not just a number. Name the rule you used — "alternate angles are equal", "because the two triangles are congruent (SAS)", "because 0.15 × 240 is less than 40". A correct number with no named reason routinely drops a mark here.
Ofqual's assessment principles push exam boards towards rewarding demonstrated reasoning, not just outcomes, which is why these instructions have become more common rather than less.
Building the habit before the exam
You cannot switch this on in May. Working shown under pressure is a habit built in ordinary homework, and the fastest way to build it is to mark your own past-paper answers against the published mark scheme. Do a question, then read the mark scheme line by line and ask one question of your own page: could an examiner point at where I earned this mark?
Two or three sessions of that and the layout changes on its own, because you have seen how thin the difference is between four marks and one.
A second habit worth having: when you check an answer and it is wrong, do not start again on fresh paper. Go back through your own working and find the line where it went wrong. That is both faster and better practice — it is exactly the skill that turns an arithmetic slip into a lost accuracy mark rather than a lost question.
Frequently asked questions
If my answer is right, do the marks for working still matter?
If the final answer is correct and the question does not say "you must show your working", full marks are usually awarded. The problem is that you cannot know in advance which answers will be correct. Showing working is insurance you buy on every question and cash in on the two or three that go wrong.
How much working is too much?
You are not writing an explanation for a reader who does not know maths. One line per genuine step, no prose, no re-copying the question. If a marker can follow the logic downwards without guessing, it is enough. Pages of narrative slow you down and win nothing.
What should I do if I get stuck halfway through?
Write down everything you can do, even if you cannot finish. Diagrams labelled with what you know, the formula you were heading for, the value you calculated before you got stuck — all of these can be method marks. A blank space is guaranteed zero; a partial attempt very often is not.
Does this apply at KS3 as well as GCSE?
Yes, and KS3 is where the habit should form. School assessments at KS3 use the same style of mark scheme, and a Year 8 who already writes formula-then-substitution-then-answer arrives in Year 10 with the single most valuable exam habit in maths already automatic.
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