2016 · Q17
A vehicle with mileage 15 km per litre contains 2 L of fuel. The vehicle gets some defect as a result of which 5 L of fuel gets wasted per hour when the engine is on. With what minimum speed the vehicle has to move to travel 20 km with the existing amount of fuel, if it travels with a uniform speed?
general-mental-abilityquantitative-aptitude
- A100 km per hour
- B120 km per hour
- C150 km per hour
- D200 km per hour
Explanation
Let the speed be v km/h; the 20 km trip then takes 20/v hours. Fuel for driving is 20/15 litres and fuel wasted is 5 x (20/v) litres, totalling the available 2 litres: 20/15 + 100/v = 2. This gives 100/v = 2/3, so v = 150 km/h. A lower speed wastes more fuel through the defect, so 150 km/h is the minimum speed that stretches the 2 litres over 20 km.