AMC8 2002

AMC8 2002 · Q21

AMC8 2002 · Q21. It mainly tests Probability (basic).

Harold tosses a nickel four times. The probability that he gets at least as many heads as tails is

Harold 抛掷一枚五分镍币四次。他得到至少与反面一样多的正面的概率是

(A) $\frac{5}{16}$ $\frac{5}{16}$

(B) $\frac{3}{8}$ $\frac{3}{8}$

(D) $\frac{5}{8}$ $\frac{5}{8}$

(E) $\frac{11}{16}$ $\frac{11}{16}$

Answer

Correct choice: (E)

正确答案：（E）

Solution

There are 16 possible outcomes: HHHH, HHHT, HHTH, HTHH, THHH, HHTT, HTHT, HTTH, THTH, THHT, TTHH and HTTT, THTT, TTHT, TTTH, TTTT. The first eleven have at least as many heads as tails. The probability is $\frac{11}{16}$.

总共有16种可能结果：HHHH, HHHT, HHTH, HTHH, THHH, HHTT, HTHT, HTTH, THTH, THHT, TTHH 和 HTTT, THTT, TTHT, TTTH, TTTT。前11种结果正面的数量至少与反面一样多。概率是 $\frac{11}{16}$。

Topics

CP.006 Probability (basic)