Mrs romney's car can travel 30 miles per gallon if she fills up the tank with 16 gallons of gas how many gallons of gas will be left in the tank after she travels 90 miles?

The “perfect world” answer is 13 gallons.

But in the real world there are too many variables to determine the precise answer without actually taking the trip. 90 miles going 60mph on flat land in 70F weather with minimal wind will leave you with a different amount of gas than 90 miles going over hills, down to valleys and back, in & out of towns, in 40 rainy weather with constant varying speeds, even when taking both trips in the same exact vehicle. Even taking the same flat 90miles 2 diff days in the same vehicle can leave you with a diff amount of gas left on each trip.

I used to work in the car industry. Never expect a vehicle to actually get the miles per gallon of gas that is stated by the manufacturer. Those are the absolute best numbers obtained in a controlled environment over multiple, multiple attempts. You will NEVER replicate in the real world what they claim on the sticker. You wouldn’t believe how many people try to return their cars because they can’t replicate the advertised miles per gallon. PS you can’t legally return a vehicle cuz it advertised 28mpg but you can only get 25mpg, especially not after months (or even years) of use!