math probability
posted by Sam on .
Four balls are selected at random without replacement from an urn containing three white balls and five blue balls. Find the probability that two or three of the balls are white.

prob (two are white) = C(4,2)((3/8)^2(5/8)^2
Prob(three are white = C(4,3)(3/8)^3(5/8)
add them up.