请教一道math题

dingzhiyin19

A contest will consist of n questions, each of which is to be answwered either true or false, anyone who answer all n questions correstly will be a winner. what's the least value of n for which the probability is less than 1/1000 that a person who randomly guesses the answer to each question will be a winner?

5    10    50     100     1000    key: 10

请大家指点！

dingzhiyin19

明白啦。谢谢！！

看来还是对题目没有理解

dreadpower

每题猜对的概率二分之一，总共n 题全猜对的概率是

（1/2）^n < 1/1000

n=10 时   ((1/2)^5)^2 = 1/(32*32) = 1/1024 < 1/1000