A bag has 4 marbles, 5 white marbles, and 6 blue marbles. Three marbles are drawn from the bag (without replacement). What is the probability that they are all the same color?
There are two possibilities for all marbles drawn to be the same color: all white or all blue. The probability of drawing 3 white marbles out of 5 white marbles is (5C3) * (1/2)^3. The probability of drawing 3 blue marbles out of 6 blue marbles is (6C3) * (1/2)^3. The total probability of drawing 3 marbles of the same color is (5C3)*(1/2)^3 + (6C3)*(1/2)^3 = 2/11.