Rather basic conversion formula.

Hey all. Good to be here. Do need some random conversion help, shouldn't be particularly difficult.

Basically I want to convert __litres per 100km__ into __miles per __**imperial** gallon

The basic conversions are:

1 mile = 1.6km

1 imperial gallon = 4.55L

1km = 0.62mi

1L = 0.22 imperial gallon.

All I want really is a formula that can convert *x*L/100km into *y*mpg

I would like to know how to justify a formula starting with just the above values. I do know what the final formula is, but the L/100km being a fraction kind of throws my understanding of how the formula would work.

Thanks a lot :)