Question

What is the Hcf of 25 and 125

Answer 1

25=5x5 -- the same as $5^2$
125=5x5x5 -- the same as $5^{3}$

As we can see there are 2 5s in the prime factors of 25 and 3 in the prime factors of 125. Therefore we pick the maximum number that is in both, which is 2, to get the HCF.

$5*5=25$

The HCF of 25 and 125 is 25.