Time for fractions!!!
I’m going to set a rate of miles per gallon and then cross multiply to get me answer.
41miles/gallon = 617.3/xgallons
617.3 multiplied by 1 and then divided by 41 = about 15.05 gallons
A reasonable estimate then is 15 and a half gallons, because rather than measuring down to the hundredths, the next closest and reasonable measurement is 15 and a half or under.
Comment if you don’t understand and I’ll try to help.