How to make formula for the fuel consumption in l/100km Hi all can someone help me with this formula that is in this pdf at the beginning.
LINK is over here.
I need to get vale in liters per 100km, and not in gallons.
Thank you.
 A: Do a little algebra with the units:
$$\frac{\text{mi}}{\text{gal}}\cdot\frac{\text{km}}{\text{mi}}\cdot\frac{\text{gal}}{\text{litre}}=\frac{\text{km}}{\text{litre}}\;,$$
so
$$\frac1{\frac{\text{mi}}{\text{gal}}\cdot\frac{\text{km}}{\text{mi}}\cdot\frac{\text{gal}}{\text{litre}}}=\frac{\text{litre}}{\text{km}}\;,$$
and
$$\frac{100}{\frac{\text{mi}}{\text{gal}}\cdot\frac{\text{km}}{\text{mi}}\cdot\frac{\text{gal}}{\text{litre}}}=\frac{\text{litres}}{100\text{ km}}\;.$$
There are exactly $1.609344 \dfrac{\text{km}}{\text{mi}}$, and the Google calculator gives a figure of $0.264172052 \dfrac{\text{gal}}{\text{litre}}$, so the conversion factor in the denominator is about $0.4251437$, and the final result is that $$\frac{\text{litres}}{100\text{ km}}\approx\frac{235.214584}{\text{miles per gallon}}\;.$$
A: Please be more explicit in your question.  The link is quite large and it is not clear what to look at.  It appears you want to convert miles per gallon to liters per 100 km.  The first think to notice is that one is distance/volume and the second is volume/distance, so they will be inverses of each other.  Then convert each unit: 1 mile = 1.609 km = 0.01609 100km; 1 gallon = 3.785 liters.  Your result should look like miles per gallon = A/(liters/100 km).  So A=(mile*liter)/(gallon * 100 km)=0.01609/3.785
