A factor of 30 is chosen at random. What is the probability, as a decimal, that it is a 2-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
