AP Statistics help?

Question

Mrs. Chavis's statistics class has 26 students in it, 14 girls and 12 boys.

She uses a calculator to select two students at random to solve a problem on the board.

(a) What is the probability that both students are girls?

(b) Given that the second student chosen is a girl, what is the probability that the first student was also a girl?

Answer 1

P(2g) = 14/26 x 13/25 = 14/50 = 28/100= 28% chance

P(g/g)= 13/25= 52/100=52% chance

Answer 2

A tree diagram might be useful here:

So the probability of 2 girls is 7/25.

The probability of the first student being a girl given that the second student is a girl is (7/25)/(7/25 + 84/325) = (7/25)/(7/13) = 13/25