IIT-JEE 1981Question 1
For a biased die the probabilities for the different faces to turn up are given below:
Face: $1,\ 2,\ 3,\ 4,\ 5,\ 6$
Probability: $0.1,\ 0.32,\ 0.21,\ 0.15,\ 0.05,\ 0.17$
This die is tossed and you are told that either face $1$ or face $2$ has turned up. Then the probability that it is face $1$ is ______.
Probability
Answer$\dfrac{5}{21}$
Solution
$P(1\mid 1\text{ or }2)=\frac{0.1}{0.1+0.32}=\frac{10}{42}=\frac5{21}$.