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

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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 $e$.

Hence, the probability is _____.

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    Does the method I describe not mean that I have ordered the choosing of the letters? (I.e one choice for the first letter implies this one must be 'a', for example) I think I meant multiplying by$3!$neglects the order?2012-11-25