JEE Main 2024 (Online) 8th April Evening ShiftQuestion 1
There are three bags $X$, $Y$ and $Z$. Bag $X$ contains $5$ one-rupee coins and $4$ five-rupee coins; Bag $Y$ contains $4$ one-rupee coins and $5$ five-rupee coins and Bag $Z$ contains $3$ one-rupee coins and $6$ five-rupee coins. A bag is selected at random and a coin drawn from it at random is found to be a one-rupee coin. Then the probability, that it came from bag $Y$, is :
Probability
Solution
$P(1\text{-rupee})\propto\frac59,\frac49,\frac39$ for X,Y,Z (total $\frac{12}9$). $P(Y|1)=\frac{4}{12}=\frac13$. Option B.