Question

The probability that, on the examination day, the student S₁ gets the previously allotted seat R₁, and NONE of the remaining students gets the seat previously allotted to him/her is

(A) 3/40 

(B) 1/8 

(C) 7/40

(D) 1/5

Answer 1

Answer is (A) 3/40

The probability that S₁ gets previously allotted S₂, S₃, S₄, and the probability S₅ does not get previously allotted seat is

1 - 1/1! + 1/2! - 1/3! + 1/4!

Hence, the required probability is