A bag contains 10 red chips and 9 blue chips.Two chips are selected randomly without replacement from the bag.What is the probability that the two chips are the same color?
A)0.529
B)0.474
C)0.526
D)0.500
E)0.263

Question

Quizplus · Accepted Answer

If the first chip is red, then there are 9 red and 9 blue chips left, so the probability that the second chip is also red is 9/18 = 1/2. Similarly, if the first chip is blue, then there are 10 red and 8 blue chips left, so the probability that the second chip is also blue is 8/18 = 4/9. The total probability is therefore:
(10/19) * (9/18) + (9/19) * (8/18) = 90/342 + 72/342 = 162/342 = 0.474.

A Bag Contains 10 Red Chips and 9 Blue Chips