So to find the factors of a number, think of all the numbers that can be multiplied together to get that number.

4 –

2*2

4*1

5 –

5*1

6 –

2*3

6*1

Since you are trying to find the least common factor, you need to find the smallest factor that 4,5, and 6 all have. The only factor they all share is 1.

Therefore, the lowest common factor is 1.

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If you ever wanted to find the least common multiple (a far more common question), just find the smallest number that 4,5, and 6 are all factors of. It’s sort of the reverse of what we did above.

The easiest way to do this is to list all the multiples of the biggest number.

For 4,5, and 6, list the multiples of 6 and see if 4 and 5 go into that number too.

6 – no

12 – 4 does, but not 5

18 – no

24 – 4 does, but not five

30 – 5 does but not 4

36 – 4 but not 5

42 – no

48 – 4 but not 5

54 – no

60 – YES

The LCM is 60.

You can often multiple the numbers together to get the LCM, but you have to be careful – sometimes there is a smaller number that all three numbers go into.

In this case, if we multipled 4,5, and 6 then you would get 120. 120 IS a multiple of all three numbers, but it is not the smallest or least common multiple.

but anyway I guess the least common factor would be the lowest factor which is a number that can divide exactly into another number exactly.

So we check with our time tables and one can see there is no other number than 1 that can do so.