单选题A jar contains 54 marbles each of which is blue, green, or white. The probability of selecting a blue marble at random from the jar is 1/3, and the probability of selecting a green marble at random is 4/9. How many white marbles does the jar contain?A6B8C9D12E18
单选题
A jar contains 54 marbles each of which is blue, green, or white. The probability of selecting a blue marble at random from the jar is 1/3, and the probability of selecting a green marble at random is 4/9. How many white marbles does the jar contain?
A
6
B
8
C
9
D
12
E
18
参考解析
解析：
Since the probability of selecting a blue marble at random from the jar is 1/3 and the probability of selecting a green marble at random from the jar is 4, the probability of selecting a white marble is 1-(1/3 + 4/9) = 1- (7/9) = 2/9. If x marbles of the 54 marbles in the jar are white, then x/54 = 2/9, 9x = 108, x = 108/9 = 12.
Since the probability of selecting a blue marble at random from the jar is 1/3 and the probability of selecting a green marble at random from the jar is 4, the probability of selecting a white marble is 1-(1/3 + 4/9) = 1- (7/9) = 2/9. If x marbles of the 54 marbles in the jar are white, then x/54 = 2/9, 9x = 108, x = 108/9 = 12.
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