What is the greatest common factor of 18 54 and 90?

Answer 1

There is no highest common multiple of any two or more numbers, for whatever multiple is stated, their LOWEST common multiple can be added to get an even higher common multiple.

However, there is a highest common FACTOR (HCF) which is the largest positive number that divides all the numbers without a remainder, and a LOWEST common multiple (LCM) which is the smallest number into which all the numbers divide without a remainder.

For 108, 54, 90:

hcf(108, 54, 90) = 18

lcm(108, 54, 90) = 540

Answer 2

The greatest common factor (GCF) is: 18