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标题: TT GWD9-23 [打印本页]

作者: dabiaoxun 时间: 2006-10-9 06:46 标题: TT GWD9-23

Q23:

When tossed, a certain coin has equal probability of landing on either side. If the coin is tossed 3 times, what is the probability that it will land on the same side each time?

A. 1/8

B. 1/4

C. 1/3

D.3/8

E.1/2

Why the answer is B, not A?

Because both sides, 1/2*1/2*1/2*2, can sb. explain it to me?

Thanks

作者: assurance 时间: 2006-10-9 19:19

because there is either all tail or all face. If all face that is 1/2*1/2*1/2+(tail)1/2*1/2*1/2=1/4

作者: robert 时间: 2006-10-9 23:14

assurance回答的正确。应该是加法原理。

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