问一道prep的数学题

dypig1234

A contest will consist of n questions, each of which is to be answered either "true" or "false". Anyone who answers all n questions correctly will be a winner. What is the least value of n for which the possibility is less than 1/1000 that a person who randomly guesses the answer to each question will be a winner?
答案：10

glaxosmith

答对几率1/2

2^3=8
2^6=64
2^9=512
2^10=1024

1/1024< 1/1000

triangel8866

这不就是求（1/2）的N次方小于1/1000么。。。。。就是2的n次方大于1000，n最小取10吧。。。。

buttonwood

顶楼上，对1024敏感的话，这题能秒杀~~