A car goes 15 miles on a gallon of octane when it is driven at 50 miles per hour. When the car is driven at 60 miles per hour, it only goes 80% as far. How many gallons of octane is needed to travel 200 miles if half the distance is traveled at 50 miles per hour and the rest at 60 miles per hour?

Correct Answer: 15
A car goes 15 km with a gallon of octane at 50 km/hr. Again, If travels with 60 km/hr, it goes 80% far as that of before. i.e. D = 80%×15 = 12 km. Now, According to question, if 100 km is travelled in 50 km/hr and another 100 km in 60 km/hr then, In 50 km/hr: 1 gallon = 15 km In 60 km/hr: 1 gallon = 12 km Hence, Total required gallons of octane is; 100/15 + 100/12 = 15 gallons.