Question

it is presentation day in class and your instructor is drawing names from a hat to determine the order of the presentations. If there are 19 students in the class, what is the probability that the first 2 presentations will be by Todd and Garrett, in that order? Express your answer as a fraction.

Answer 1

Okay, here we have this:

Considering the provided information, and that order matters here, we are going to use permutation, so we obtain the following:

n=19

r=2

And, let's replace in the following formula:

$\text{nPr}=\frac{n!}{(n-r)!}$

Replacing:

$\begin{gathered} 19P2=\frac{19!}{(19-2)!} \\ =\frac{19!}{17!} \\ =342 \end{gathered}$

And, as the number of ways of select those two are: 1

We obtain finally that the probability is 1/342.