Every prime number greater than 10 has a digit in the ones place that is included in which set of numbers below?

So we can start with the full of possibilities and eliminate them one by one.

The full set is {0,1,2,3,4,5,6,7,8,9}.

Now we know that any prime greater than 2 is odd as otherwise it would have 2 as a factor, so we can eliminate all of these digits that would be an even number, leaving:

{1,3,5,7,9}

We also know that any prime greater than 5 cannot be a multiple of 5 and that all numbers with 5 in the digits are a multiple of 5, so we can eliminate 5.

{1,3,7,9}

We know that 11,13,17 and 19 are all primes, so we cannot eliminate any more of these, leaving the set:

{1,3,7,9} as our answer.

The right answer should be 6 but your not very specific