Question 854941
If the school was 10 miles from the student's home,
it would take him {{{10miles/5mph=2hours}}} to bike to school,
and {{{10miles/10mph=1hours}}} to bike home.
The round trip would be {{{2*10miles=20miles}}}
and it would take {{{2hours+1hour=3hours}}} .
the average speed would be
{{{20miles/3hours=highlight(6.3mph)}}} (rounded).
 
The 10 mile distance was made up, but the calculation would be the same with any distance.
We could say, it is {{{d}}} miles,
so the times in hours would be {{{d/5}}} and {{{d/10}}}.
The round trip would be {{{2d}}} miles,
and it would take {{{d/5+d/10=2d/10+d/10=3d/10}}} hours.
Them, the speed (in mph) would be calculated as
{{{2d/(3d/10)=2d*(10/3d)=20d/30d=20/3=6.3}}} .
The distance cancels out, and it was easier to understand and calculate by making {{{d=10miles}}} .