An unbiased coin is tossed.

Question

An unbiased coin is tossed. If the outcome is a head then a pair of unbiased dice is rolled and the sum of the numbers obtained on them is noted. If the toss of the coin results in tail then a card from a well-shuffled pack of nine cards numbered 1, 2, 3, \ldots \ldots , 9 is randomly picked and the number on the card is noted. The probability that the noted number is either 7 or 8 is :

Accepted Answer

$$P\left( A \right) = {1 \over 2} \times {{11} \over {36}} + {1 \over 2} \times {2 \over 9} = {{19} \over {72}}$$

Solutions · 1