Why does my child mix up the HCF and the LCM?
Your child mixes up the highest common factor and the lowest common multiple, such as giving 36 as the HCF of 12 and 18.
Why children do it
The two have similar names, and they're usually learnt together. The highest common factor goes into both numbers, so it's never bigger than them. The lowest common multiple comes from both, so it's never smaller. For 12 and 18, the HCF is 6 and the LCM is 36.
How to help at home
Ask: does a factor go into the number, or does a multiple come from it? A common factor is never bigger than the numbers.
The right way
Find the highest common factor of 12 and 18.
- 66 goes into both 12 and 18, and nothing bigger does. Their LCM would be 36.
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