Lowest Common Multiples (LCM)

The multiples are basically the times tables of the numbers you are considering – remember, you MUST include the number itself, e.g. the first 5 multiples of 8 are: 8, 16, 24, 32 and 40.

The Lowest Common multiple will be the first number of the times table which is shared by all the numbers you are considering.

Some of the common multiples of 2 and 5 are: 10, 20, 40, 50, 100, 500 etc. but the Lowest Common Multiple would be…

2x: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20

5x: 5, 10, 15, 20, 25, 30…

There are going to be lots of numbers that appear in both times tables, but the lowest one you can see is 10.

The process for finding factors and Multiples can be very time consuming, especially when the numbers are so much larger – so we need to consider a more efficient method for finding the HCF and LCM. This is where the Prime Factorisation method comes in.