# Probability question on picking letters

5 letters: a, b, c, d, e I randomly pick 3 letters, whats the chance of having a and b in those 3 letters

-

You have a total of $5$ letters and you are choosing $3$ from them. Hence, the total number of ways of choosing three letters is $\dbinom{5}3$.
Number of ways in which you have $a$ and $b$ as two of your three letters is $\dbinom{3}1$, since the third letter you can choose from any of the remaining three letters $c$, $d$ and $e$.
@CAF Yes. In fact that is how I have derived. However, I don't see why you want to divide by $3!$. –  user17762 Nov 24 '12 at 23:38