Question

Fuel efficiency in Europe is commonly defined as fuel consumption per 100 [km]. An American car has a fuel efficiency of 32 [mi/gal) and a European car has a fuel efficiency of 5.2 [L/100 km). Which car is more efficient?

Answer 1

The European car is more efficient (5.2 vs 7.35 L/100km)

Step-by-step explanation:

To compare the two efficiencies we have to have them in the same units.

We have that 1 mi. is equal to 1.61 km and 1 gal is 3.785 litres.

The american car efficiency can be expressed as:

`Ef=32(mi)/(gal)*(1.61km)/(1 mi)*(1gal)/(3.785\,L)   \\\\Ef=13.6\,km/L`

We calculate the amount of kilometers the car can make with one litre of fuel. To know the efficiency in L/(100 km) we have to rearrange the expression:

`\eta=(1)/(13.6)(L)/(km) *(100)/(100)=(100)/(13.6)*(L)/(100\, km) \\\\\eta=7.35 \, (L)/(100\, km)`

We know now that the american car consumes 7.35 L per 100 km, which is higher than the european car.

So, the European car is more efficient (5.2 vs 7.35 L/100km)