The Most Common Silly Mistakes in Arithmetic Sections (and How to Catch Them)

Losing Marks You Already Knew

In arithmetic sections of entrance exams, a large share of lost marks does not come from not knowing the method — it comes from small, repeatable slips made while executing a method the student already understands. The good news is that these slips fall into a fairly short list, which makes them easy to watch for once a student knows what to look for.

The Usual Suspects

Misreading the question: Solving for "cost price" when the question asked for "selling price," or missing a "not" or "except" in the wording.
Sign and operation errors: Adding instead of subtracting, or dropping a negative sign midway through a calculation.
Unit mismatches: Mixing hours and minutes, or metres and centimetres, without converting first.
Copying errors: Writing 76 instead of 67 when transferring a number from the question to rough work.
Wrong final step: Solving correctly but selecting the wrong option because the answer was rounded, or a percentage was left as a decimal.
Table and fact slips: Small errors in multiplication tables or squares that snowball through a multi-step problem.
Order of operations: Solving addition before multiplication in an expression that needs BODMAS applied correctly.

Why These Happen Even to Strong Students

These mistakes tend to increase under time pressure, which is exactly the condition of a real exam. A student who is accurate in untimed homework can start making these slips the moment a clock is running. This is why silly mistakes are not really about knowledge — they are about attention management under pressure, and they need to be practiced under similar pressure to be fixed.

Habits That Catch Them Before Submission

Underline the actual question before starting any calculation, especially the unit or quantity being asked for.
Write numbers clearly in rough work, leaving space so a "1" is never confused with a "7."
Do a units check as the very last step — does the final answer's unit match what was asked?
Re-read the question after solving, not just before, to confirm the answer matches what was actually asked.
Estimate first: a rough mental estimate before calculating catches wildly wrong final answers immediately.

Building the Habit Over Time

None of these habits are instinctive — they have to be practiced deliberately, ideally during regular timed practice rather than only in real exams. A short checklist run mentally in the last 20 seconds on each arithmetic question, built through repetition, prevents many of these mistakes from ever reaching the answer sheet.