A die is thrown twice and the sum of the numbers appearing is observed to be 6. The conditional probability that the number 4 has appeared at least once, is
Answer & explanation
Correct answer: option 2
Consider the following events:
A = Number 4 appears at least once,
B = The sum of the numbers appearing is 6.
∴ Required probability
$= P(A/ B)$
= Probability of occurrence of A when B is taken as the sample space
Number of elementary events favourable to
$=\frac{\text{A which are favourable to B}}{\text{Number of elementary events favourable to B}}=\frac{2}{5}$