Why do IGCSE maths students lose marks on questions they actually know how to do?

Most Cambridge IGCSE Maths marks are lost to process errors, not hard questions.

Students drop marks on questions they fully understand because small, repeatable mistakes compound under exam pressure. A sign slip in substitution, a premature round mid-working, or a misread command word can each cancel an otherwise correct answer.

Cambridge IGCSE papers award method marks and accuracy marks separately. One careless error on an early step can wipe out follow-through marks on every step after it. The grade damage is far larger than the mistake itself.

Three errors appear most often on candidate scripts. Here is what they are and how to fix each one.

• Negative sign slips: write brackets around every substituted value, such as (-3)²
• Premature rounding: keep intermediate values to four decimal places, round only at the end
• Misread instructions: underline the command word and accuracy requirement before starting

Sign errors alone are the single most recorded mistake in Cambridge IGCSE Maths. Substituting x = -3 into x² without brackets gives -9 instead of 9. One habit removes this entirely.

Rounding errors usually appear in two ways. Students round too early, then carry the accumulated error forward. Or they round to the wrong precision at the end, such as giving two significant figures when the question asks for three. The mark scheme awards zero for the accuracy mark in both cases, even when the method is correct.

Misreading instructions is painful because the maths is often right. A question asking for the radius gets answered with the diameter. A question asking to factorise gets solved instead. Underlining command words takes under five seconds and removes this category almost entirely.

Two further habits protect marks across the whole paper. First, show every step of your working. IGCSE tutoring specialists consistently see students lose method marks simply because correct intermediate steps were not written down. Second, check your calculator mode before any trigonometry question.

Building these habits requires deliberate practice, not just awareness. After each past paper, sort every lost mark by error type rather than by topic. If sign slips and rounding account for most losses, those process areas become the revision priority, not algebra or statistics as a subject.

Our blog has a full breakdown of each error type, a five-step working framework, and guidance on using mock exam feedback to identify your specific patterns before your next sitting.