A and B appear for an interview for two vacancies in the same post. The probability of A’s selection is 1/6 and that of B’s selection is 1/4. Find the probability that
(i) both of them are selected
(ii) only one of them is selected
(iii) none is selected
(iv) at least one of them is selected.
Given : A and B appear for an interview ,then P(A) = and P(B) = P() = and P() =
Also, A and B are independent .A and not B are independent, not A and B are independent.
To Find: i) The probability that both of them are selected.
We know that, P( both of them are selected) = P( A B) = P(A) P(B)
=
=
Therefore , The probability that both of them are selected is
ii) P(only one of them is selected) = P(A and not B or B and not A)
= P(A and not B) + (B and not A)
= P( A ) + P(B )
= P(A) P() + P(B) P()
= + )
= +
=
Therefore, the probability that only one of them Is selected is
iii)none is selected
we know that P(none is selected) = P()
= P() P()
=
=
Therefore , the probability that none is selected is
iv) atleast one of them is selected
Now, P(atleast one of them is selected) = P(selecting only A ) + P(selecting only B) + P(selecting both)
= P(A and not B) +P (B and not A) +P (A and B)
= P( A ) + P(B ) + P( A B)
= P(A) P() + P(B) P() + P(A) P(B)
= + )+
= + +
=
Therefore, the probability that atleast one of them is selected is