On the
other hand, calculating travel times in metric is much easier.
The standard highway speed in 100 kph, so a 500 km trip should
take 5 hours.

I like to do math with simple numbers like that.


Stupid example, though. If you're going 100 MPH, a 500 mile
trip also takes five hours. If you're only using one set of
units, it doesn't make any difference what they are.