To determine which car has the greatest efficiency, we need to analyze the fuel economy (distance traveled per liter of fuel) of each car. Efficiency in this context can be simplified to the kilometers traveled per liter of fuel, irrespective of the weight of the car, since the question does not ask for power-to-weight ratio or other performance metrics.
Here are the efficiencies as given:
- 1,200 kg car that travels 15 km per liter of fuel: 15 km/l
- 900 kg car that travels 20 km per liter of fuel: 20 km/l
- 900 kg car that travels 15 km per liter of fuel: 15 km/l
- 1,200 kg car that travels 20 km per liter of fuel: 20 km/l
Now let's compare the fuel economies:
- The 1,200 kg car with 15 km/l has an efficiency of 15 km/l.
- The 900 kg car with 20 km/l has an efficiency of 20 km/l.
- The 900 kg car with 15 km/l has an efficiency of 15 km/l.
- The 1,200 kg car with 20 km/l has an efficiency of 20 km/l.
From the comparisons:
- The 900 kg car that travels 20 km/l and the 1,200 kg car that travels 20 km/l both have the same fuel efficiency of 20 km/l, which is greater than the efficiencies of the other two cars.
So, the two cars with the greatest efficiency are:
- The 900 kg car traveling 20 km per liter of fuel
- The 1,200 kg car traveling 20 km per liter of fuel
If the question requires choosing just one option, you could select the 900 kg car that travels 20 km per liter of fuel for slightly higher efficiency relative to its mass.
Therefore, the car with the greatest efficiency is: a 900 kg car that travels 20 km per liter of fuel.