Probability Query

Question

A box contains 3 red chips and 7 white chips. A chip is selected at random, its color noted and is set aside. Then a second chip is selected and its color noted. Let W be the number of white chips picked. Find the probability distribution of W and then compute E(W)

Answer 1

White chips selected probability

0 RR 3/10 * 2/9 = 0.067

1 WR or RW 7/10 * 3/9 + 3/10 * 7/9 = 0.47

2 WW 7/10 * 6/7 = 0.6

E(W) = 0*0.067 + 1*0.47 + 2*0.6 = 1.67