Answer:
The answer to your question is 11.25 gal
Explanation:
Data
Capacity = 30 gal of gasoline
Consumption = 4.5 gal per 100 km
Process
1.- Calculate the gasoline used in 250 km
4.5 gal -------------------- 100 km
x ------------------- 250 km
x = (250 x 4.5) / 100
x = 1125 / 100
x = 11.25 gallons
2.- Calculate the gasoline that remain in the tank
Gasoline in the tank = Full tank - Gasoline used
= 30 gal - 11.25 gal
= 18.75 gal
3.- Calculate the gallons needed to refill the tank.
The gasoline needed to refill the tank is that same that the gasoline used during the first 250 km traveled.