Two unbiased dice are thrown. Find the probability that the sum of the numbers appearing is 8 or greater, if 4 appears on the first die.
Two die having 6 faces each when tossed simultaneously will have a total outcome of 62=36
Let P(A) be the probability of getting a sum greater than 8.
Let P(B) be the probability of getting 4 on the first die.
The sample space of B = {(4,1),(4,2),(4,3),(4,4),(4,5),(4,6)}
Let 
be the probability of getting 4 on the first die and the sum greater than or equal to 8
The sample space of 
Tip – By conditional probability, 
where 
is the probability of occurrence of the event A given that B has already occurred.
The probability that sum of the numbers is greater than or equal to 8 given that 4 was thrown first:
1