JEE Main 2021 (Online) 3rd August Evening ShiftQuestion 1
A dice is thrown twice. If $A$ is the event that the sum of numbers appearing on them is $7$ and $B$ is the event that number $5$ appears at least once, then $P(B|A)$ is equal to
Probability
Solution
Sum 7: $(1,6),(2,5),(3,4),(4,3),(5,2),(6,1)$, so $n(A)=6$. Those containing a 5: $(2,5),(5,2)$. $P(B|A)=2/6=\frac13$. Option B.