Help with math, explanations as opposed to answers thanks! best=10 pts!?

Question

Karen, David, Jenny, George, and Sam are in a band. They need to choose a guitarist, a piano player, and a drums player.
a) Make a tree of the possible choices for these 3 positions. (if possible)
b) In how many ways can the 3 positions be chosen?
c) What is the probability that Jenny is chosen to play the piano?

Answer 1

Let's start by choosing a drummer: Their are 4 different possibilities.

Once we choose the drummer we need to assign the other 3 people to the other 2 instruments. Let's start by choosing a pianist. There are only 3 possible outcomes.

Finally we have 2 people competing for 1 instrument. There are 2 possible outcomes.

So we have 4 X 3 X 2 = 24 possibilities.

a. 24 possibilities
b. 24
c. If we choose the pianist first then it is obvious that it is 1/4.