What numbers are not factors of 60 and 70?

Answer 1

The factors that both 60 and 70 have are 1, 2, 5, and 10. All of these are also factors of 10. So, there is not a number that is a factor of 60 and 100 but is not a factor of 100.

Answer 2

The common factors of 60 and 70 are 1, 2, 5 and 10. These are also factors of 100. I suspect the problem was originally 60 and 72. In that case the answer would be 12.

Answer 3

Anything but these:

The factors of 60 are:

1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60

The factors of 70 are:

1, 2, 5, 7, 10, 14, 35, 70

Answer 4

Anything that isn't 1, 2, 5 or 10.

Answer 5

8