≫ 1 mile / 2 km
    1 mi / 2 km
     = 0.804672

Great, but it would be nice to show the result's unit.

  ≫ 1/2km
    1 / 2 km
     = 0.5 km⁻¹

It's been a long while since I did any real maths, so I'm slightly stumped as to why the -1 exponent is there.