A coin is tossed.

Question

A coin is tossed. If head, a pair of dice is rolled and the sum noted; if tail, a card from 9 numbered cards is picked. Find the probability the noted number is 7 or 8.

Accepted Answer

$P(\text{sum}=7\text{ or }8) = \dfrac{6}{36}+\dfrac{5}{36}=\dfrac{11}{36}$. $P(\text{card}=7\text{ or }8)=\dfrac29$.

$$P = \frac12\times\frac{11}{36}+\frac12\times\frac29 = \frac{19}{72}$$

Solutions · 1