Question

In a school there are 1000 students, out of which 430 are girls. It is known that out of 430, 10% of the girls study in class XII. What is the probability that a student chosen randomly studies in class XII given that chosen student is a girl ?

Answer 1

Let A be the event that a student chosen randomly studies in class XII and B be the event that the randomly chosen student is a girl.

$n(A\cup B)=10$% of $430=43$

$n\left(B\right)=430$

Therefore,

Required probability = $P\left(A/B\right)=\frac{n(A\cap B)}{n\left(B\right)}=\frac{43}{430}=\frac{1}{10}$