# Probability question please help

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• November 19th 2012, 12:49 PM
Nasc0
Probability question please help
if i guess at five choice questions. each question has 5 anwsers to pick from. whats the probability that i l get three correct? tell me how u did it also thanks.
• November 19th 2012, 01:19 PM
skeeter
Re: Probability question please help
probability problems go in the statistics forum
• November 19th 2012, 01:57 PM
Plato
Re: Probability question please help
Quote:

Originally Posted by Nasc0
if i guess at five choice questions. each question has 5 anwsers to pick from. whats the probability that i l get three correct? tell me how u did it also thanks.

If $p$ is the probability of success and $N$ is the number of trials then the probability of exactly $k$ successes, where $0\le k\le N$, is $\binom{N}{k}p^k(1-p)^{N-k}$.