Answer: 175 gallons of fuel
Explanation:
Quantity of fuel to fly = 80 gallons
Distance travelled using 80 gallons of fuel = 320 miles
Therefore, distance travelled by the flight in 1 gallon of fuel = 320 / 80
= 4 miles/gallon
Now, Quantity of fuel needed for a 700 mile flight = 700 / 4
= 175 gallons
Therefore, 175 gallons of fuel is needed for a 700 mile flight.