Q. 15

# The probability that a student is not a swimmer is 1/5. Then the probability that out of five students, four are swimmers is

A.

B.

C.

D. None of these

Answer :

In this question, let us assume X represent the number of students out of 5 who are swimmers

Also, the repeated selection of students who are swimmers are the Bernoulli trials

Thus, probability of students who are not swimmers

Clearly, we have X has the binomial distribution where n = 5

And,

∴

_{Hence, probability that four students are swimmers = P (X = 4)}

∴ option A is correct

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