## Elementary Statistics (12th Edition)

$0.917$
We know that $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$ and by the inclusion-exclusion principle:$P(A \cup B)=P(A)+P(B)-P(A\cap B)$. A:responded B:his/her age is between 18 and 21. By checking the data: $P(A)=\frac{1049}{1205}$ $P(B)=\frac{275+278}{1205}$ $P(A\cap B)=\frac{255+245}{1205}$ Therefore the probability of the person responding or his/her age being between 22 and 29 or between 30 and 39: $P(A \cup B)=\frac{1049}{1205}+\frac{275+278}{1205}-\frac{255+245}{1205}=\frac{1102}{1205}\approx0.917$