Simplest form: the right fraction, the wrong final answer
Your child's working is correct and the final answer reads 3/6 when the question asked for the answer in its simplest form. The value is right, but the instruction was not followed, so the answer mark can be lost. It is one of the most avoidable ways to drop a mark.
What it looks like
A jug was 5/6 full of juice. Farah poured out an amount equal to 1/3 of the jug's capacity. What fraction of the jug was filled with juice then? Give your answer in its simplest form.
- 1/3 = 2/6
- 5/6 − 2/6 = 3/6
- 3/6 = 1/2 (divide top and bottom by 3)
Why 3/6 is wrong: The subtraction was correct, but 3/6 was not simplified even though the question asked for simplest form.
Why children do it
- Once the calculation is done, your child feels the question is finished and moves on.
- The instruction "in its simplest form" is often at the very end of the question and is easy to skip.
- Children do not always check for a common factor when the numbers are small and the fraction looks tidy.
How to fix it at home
- Make a last line part of every fraction answer: "Can I divide the top and bottom by the same number?"
- Ask your child to box "simplest form" in the question whenever it appears.
- Practise spotting common factors quickly: both even, both end in 0 or 5, digits that add up to a multiple of 3.
Questions parents ask
Will the marker accept 3/6 if the question says simplest form?
You should not count on it. When the question asks for simplest form, an unsimplified answer does not follow the instruction and can lose the answer mark.
Do ratios need to be in simplest form too?
When the question asks for a ratio in its simplest form, yes. The same last-line check works for ratios.
Other careless mistakes
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