Why does my child think the LCM of 6 and 8 is 48?
Your child multiplies the two numbers to find the lowest common multiple, such as 6 × 8 = 48 for the LCM of 6 and 8.
Why children do it
Multiplying the two numbers always gives a common multiple, so it seems to be the answer. But it often isn't the lowest: 24 is in both lists of multiples (6, 12, 18, 24 and 8, 16, 24), well before 48.
How to help at home
Ask them to list the first few multiples of each number and find the first one in both lists.
The right way
Find the lowest common multiple of 6 and 15.
- 6 = 2 × 3The prime factors of 6.
- 15 = 3 × 5The prime factors of 15.
- 2 × 3 × 5 = 30Use every prime, as many times as it appears in either.
- 30So the LCM is 30.
Find out where your child is
A free maths check, in about 15 minutes, shows what your child knows and the mistakes they make. No sign-up.
Start the free check