2道数学题

real_arsen_acUID: 2413853

The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to tossed 3 times, what is the probability that on at least one of the tosses the coin will turn up tails?
a.1/8 b.1/2 c.3/4 d.7/8 e.15/16
答案是d.7/8

In a nationwide poll, N people were interviewed. If 1/4 of them answered yes to question 1, and of those, 1/3 answered yes to question 2, which of the following expressions represnets the number of people interviewed who did not answer yes to both questions?
a.N/7 b.6N/7 c.5N/12 d.7N/12 e.11N/12
答案是e.11N/12

TyliayssUID: 185761

1. 1-1/2*1/2*1/2

real_arsen_acUID: 2413853

楼上能稍微解释一下吗？谢谢！

minami242UID: 2517882

就是把三次都得到tail的几率减去。

哪位能回答一下我关于gmat笔试模考自己怎么算分的问题？

TyliayssUID: 185761

好像OG黄本后面有算分办法的吧。。。。

lykid1987UID: 2302705

2。题目意思是没有两题都回答yes（both是部分否定的）
N*（1-1/3*1/4）

aiwen6UID: 2526420

。。。。。。。。