What is the HCF of 84 and 108?

To do this, you first have to break 84 and 108 down into their prime factors:

84 = 2x2x3x7

108 = 2x2x3x3x3

The next step is to identify any common prime factors. In this case both numbers have two 2s and a 3 as prime factors. Multiply these together and you get 12.

Therefore the HCF of 84 and 108 is 12.