Mark (√) against the correct answer in each of the following:
A die is thrown twice, and the sum of the numbers appearing is observed to be 7. What is the conditional probability that the number 2 has appeared at least one?
The die is thrown twice,
So the favourable outcomes that the sum appears to be 7 are
(1,6), (2,5), (3,4), (4,3), (5,2) and (6,1)
Out of these 2 appears twice,
So the probability that 2 appears at least once is:
= 
⇒ 
1