My car has a gas problem maybe.?

I own a 1994 chevy camaro v6 3.4L vehicle thats nice. But one thing that makes me wonder Is that I bought this car with a half a tank of gas but the wierd thing Is that this car only had 38 miles put on the car and now the half a tank of gas Is missing. Which would mean that the car would get 76 miles on a full tank of gas. Obviously there Is something wrong there when the car Is supposed to get 19mpg. Thats like saying It Is only a 3.5 gallon car size tank. Well I am wondering whats wrong because the car was averaging 50mph speeds thats basically lame. Like how could I afford to drive this car If thats really the case. Anyone know what could be wrong or what I need to do. Maybe It needs a new part. Whats your opinion.