Hi Mason,

I expect that you are to use each digit exactly once. The number of 6 digit numbers you can make from the digits 1, 2, 5, 6, 7 and 9 with each digit used only once is the number of permutations of 6 items taken 6 at a time.

An integer is divisible by 6 is and only if it is divisible by both 2 and 3. An integer is divisible by 2 if and only if its units digit is divisible by 2. In your list of digits only 2 and 6 are divisible by 2. How many in your list of 6 digit numbers have a 2 as the units digit? How many have a 6? For divisibility by 3 look at my response to Ben.

Penny