Calculation slips: right method, wrong arithmetic
Your child sets up the question correctly and then a single arithmetic step goes wrong, such as a missing zero in long division. These are the marks parents call careless, but the same slip tends to come back in the same place. Paper 1 is done without a calculator, so these slips cost the most there.
What it looks like
A school collected 2142 cans for recycling. The cans were packed equally into 7 boxes. How many cans were there in each box?
- 21 ÷ 7 = 3, remainder 0
- Bring down 4: 4 ÷ 7 = 0, remainder 4 (write 0 in the answer)
- Bring down 2: 42 ÷ 7 = 6
- 2142 ÷ 7 = 306
Why 36 cans is wrong: When 4 could not be divided by 7, the 0 was not written in the answer, so 306 became 36.
Why children do it
- When a digit "doesn't go", children move on to the next digit without writing 0 in the answer.
- Your child is thinking about the method, so the arithmetic gets less attention.
- Working is squeezed into small spaces, and digits drift out of their columns.
How to fix it at home
- Teach the rule: every digit you bring down puts one digit in the answer, even if it is 0.
- Ask your child to check every division by multiplying back: 36 × 7 = 252, which is nowhere near 2142.
- Estimate before calculating: 2142 ÷ 7 is about 2100 ÷ 7 = 300, so the answer must be around 300.
- Use squared paper for long division so each digit stays in its column.
Questions parents ask
Is my child just careless?
Rarely. Most "careless" mistakes repeat in the same kind of step, which makes them habits. A habit can be practised away; general carefulness is much harder to train.
Should my child check every answer?
Checking every step takes too long in the PSLE. A quick estimate and multiplying back on division answers catches most slips in seconds.
Where it shows up
Other careless mistakes
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