7 Common A-Level Maths Mistakes (and How to Avoid Them)

At A-Level, the difference between a B and an A is rarely a topic you've never seen — it's a handful of avoidable mistakes repeated across the paper. Here are the seven we see most often.

1. Sign errors when expanding brackets

Negatives distributed carelessly wreck otherwise perfect solutions. Write each step; don't skip lines to "save time".

2. Forgetting the constant of integration

Every indefinite integral needs +C. It's one mark each time — and it adds up.

3. Dropping units or exact values

If a question asks for an exact answer, a rounded decimal loses marks. Leave surds and fractions as they are unless told otherwise.

4. Misreading the command word

"Show that", "hence", and "prove" all demand different things. "Hence" means you must use the previous part.

5. Calculator mode and radians vs degrees

Half of trig and calculus questions assume radians. Check your calculator mode before every session and every exam.

6. Not defining variables

In mechanics and statistics, undefined variables cost method marks. State what each letter means before you use it.

7. Skipping the "check" step

Substitute your answer back in, or sanity-check the size of the number. A negative length or a probability above 1 should stop you immediately.

How to actually fix these

Keep a mistake log for two weeks. You'll notice the same two or three errors dominate — and once you're aware of them, they disappear fast.