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.

Answer 1

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)