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?

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

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:

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:

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)

answer carbon and three oxygen atoms;

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.