Question

The probability of taking examination in class by a teacher is 1/5. If a student is absent two times then probability that he was absent at least in one examination is –

(A) 9/25

(B) 11/25

(C) 13/25

(D) 23/25

Answer 1

Answer is (A) 9/25

Let student is absent in first examination, event is collect E and absent in 2nd is F, then

According to question

Probability that students is absent in at least one exam. 

= 1 – (Prob. that student is absent in both the exams)

Thus, this is prob. that student appear at least one examination.