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苹果虫

A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow.  If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

 

A.      3/64

B.      1/20

C.      1/16

D.     1/12

E.      1/8

Answer: B

我的算法是4乘3/C16取2=1/10（不知道杂子能打出来，只能这样了，看的懂吧？）