What is the LCM of 105 and 63?

Answer 1

Using digital roots (adding all the digits in a number up until you get a single digit) we can see that:

105: 1+0+5 = 6

63: 6+3 = 9

If both digital roots equal 3,6,and/or 9 then the LCM is always 3.

The Normal Way:

A few Multiples of 105:

105 / 5 = 21

21 / 7 = 3

3,5,7,21,105

A few Multiples of 63:

63 / 3 = 21

21 / 7 = 3

3,7,21,63

So as you can see, the LCM is 3.