30% of airlines have WiFi and 70% have free snacks. The question asks for the greatest possible percentage of airlines that have both WiFi and free snacks.
Glance at the answers. They're really far apart, so estimate and logic this out.
Imagine that you have 100 airlines. 30 of them offer WiFi and 70 of them offer snacks, but you don't know the overlap between who offers WiFi and who offers snacks.
However, it's true that 30 out of the 100 offer WiFi, so at most, those 30 airlines offer both WiFi and snacks. It would be impossible for 40 airlines to offer both, since exactly and only 30 of them offer WiFi in the first place. Eliminate answers (C), (D), and (E).
The two remaining answers are 21% and 30%. Is it possible that all of the companies who offer WiFi also offer snacks?
Since the number of airlines that offer WiFi is less than the number of airlines that offer snacks, it is possible that all of the companies that offer WiFi also offer snacks. The problem offers no other constraints that limit this possibility.
If all 30 airlines that offer WiFi also offer snacks, then 30 out of 100 airlines is the greatest number of airlines that offer both. So the greatest possible percentage is 30 out of 100 or 30%.
The correct answer is (B).
