Question

If the probability that a student is not a swimmer is 1/5, then the probability that out of 5 students one is swimmer is

• A. ${ } ^ { 5 } C _ { 1 } \left( \frac { 4 } { 5 } \right) ^ { 4 } \left( \frac { 1 } { 5 } \right)$
• B. ${ } ^ { 5 } C _ { 1 } \frac { 4 } { 5 } \left( \frac { 1 } { 5 } \right) ^ { 4 }$
• C. $\frac { 4 } { 5 } \left( \frac { 1 } { 5 } \right) ^ { 4 }$
• D. None of these

Answer 1

Answer: (B)

${ } ^ { 5 } C _ { 1 } \frac { 4 } { 5 } \left( \frac { 1 } { 5 } \right) ^ { 4 }$

Answer 2

Required probability = ${ } ^ { 5 } C _ { 1 } \left( \frac { 4 } { 5 } \right) \left( \frac { 1 } { 5 } \right) ^ { 4 }$

{Here strictly one is swimmer}