A factor of thirty is chosen at random what's the probability that it's a two digit number

The positive whole-number factors of 30 are:

1, 2, 3, 5, 6, 10, 15 and 30.

So, there are 8 of them. Of these, 3 have two digits. Writing each factor on a slip of paper, then putting the slips into a hat, and finally choosing one without looking, get that

P (factor of 30 chosen is a 2-digit number) = number of two-digit factors : number of factors

=38=3*.125=.375 (37.5%)