A bag contains 5 red, 9 white, and 10 blue marbles. Suppose you choose a marble from the bag and then choose another marble without replacing the first one. Find the probability of picking the same color both times.

Answer 1

= Prob(both red) + Prob(both white) + prob(both blue)
= (5/24)(4/23) + (9/24)(8/23) + (10/24)(9/23)
= 5/138 + 3/23 + 15/92
= 91/276