SOLUTION: In a group of 20 students, five do not have a mobile phone. If three students are selected at random from the group, work out the probability that exactly one of these three studen

Question 936015: In a group of 20 students, five do not have a mobile phone. If three students are selected at random from the group, work out the probability that exactly one of these three students does not have a mobile phone.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
In a group of 20 students, five do not have a mobile phone. If three students are selected at random from the group, work out the probability that exactly one of these three students does not have a mobile phone.
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Binomial Problem with n = 3 and p(no phone) = 5/20 = 1/4 ; p(phone) = 3/4
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P(x = 1) = 3C1(3/4)(1/4)^2 = 3*3/64 = 9/64
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Cheers,
Stan H.
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