math
posted by Diana .
A box contains three white balls and two red balls. A ball is drawn at random from the box and not replaced. Then a second ball is drawn from the box. Draw a tree diagram for this experiment and find the probability that the two balls are of different colors.

there are only 4 cases:
WW  prob is (3/5)(2/4) = 6/20
WR  prob is (3/5)(2/4) = 6/20
RW  prob is (2/5)(3/4) = 6/20
RR  prob is (2/5)(1/4) = 2/20
so different colours are : WR and RW = 6/20 + 6/20 = 12/20 = 3/5
(notice the 4 cases add up to 1)