lowest common factor , is it the same as lowest common multiple

[ggirl]

and how do i explain it to ds?
says he did it before half term and can't remember now

No, but usually you have to find the highest common factor and lowest common multiple.
The lowest common multiple of 3 and 4 is 12. Write out the 3s (3,6,9,12,15) and the 4s (4,8,12,16) until you get one which is in both.
Highest common factor of 20 and 28 is 4. It is the highest number which fits into both.

The lowest common factor will be 1.

thank you