Now, the sample space of the experiment is S = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
Then
A = {2, 4, 6, 8, 10},  B = {4, 5, 6, 7, 8, 9, 10}
and
A ∩ B = {4, 6, 8, 10}
Also
P(A) = 5
7
4
, P(B) =
and P(A
B)
10
10
10
∩
=
Then
P(A|B) =
4
P(A
B)
4
710
P(B)
7
10
∩
=
=
Example 4 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 the chosen student is a girl Solution Let E denote the event that a student chosen randomly studies in Class XII
and F be the event that the randomly chosen student is a girl