Probability
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Q.

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

 A.

\(^5C_4\left(\dfrac{4}{5}\right)^2\left(\dfrac{1}{5}\right)\)

 B.

\(\left(\dfrac{4}{5}\right)^2\left(\dfrac{1}{5}\right)\)

 C.

\(^5C_4\left(\dfrac{1}{5}\right)\left(\dfrac{4}{5}\right)^4\)

 D.

None of these

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Solution:
Option(C) is correct

4 students out of 5 can be selected in \(^5C_4\) ways.

Probability of a student being not a swimmer \(=\dfrac{1}{5}\)

Probability of a student being a swimmer

 \(=1-\left(\dfrac{1}{5}\right)=\dfrac{4}{5}\)

Required probability

\(=^5C_4\times\left(\dfrac{1}{5}\right)\times \left(\dfrac{4}{5}\right)^4\)


(3) Comment(s)


Gaurav Karnani
 ()

question language has ambiguity



Sudeep Sahu
 ()

can anyone explain me this problem in more detail....?


Jyothi
 ()

its based on a formula ncr*(p)^r(1-p)^n-r

p= probability of favourable outcomes

n= total events

r=favorable events