Question 1020821
{{{(70km/hour)(1mile/1.6km)=(43.75mi/hr)}}}

{{{(43.75mi/hr)(2hrs)=(87.5miles)}}}

See the first line - the process is called dimensional analysis. You want to be sure to line up your units in a way that cancels what you are getting rid of (km here) but leaves what you want (here miles). 

You can use this to convert miles per hr to feet per second, which is useful. Or any conversion you want.