Question 711756
<pre>
The other tutor used decimals and rounded off, making his answer off
a little.  I'll use fractions.

We use two formulas:

Distance = Rate × Time

Average Rate = Total Distance ÷ Total Time

When you went 30 minutes (half an hour) at 60 mph,
you went 60×{{{1/2}}} = 30 miles  

When you went 10 minutes ({{{1/6}}} of an hour) at 38 mph,
you went 38×{{{1/6}}} = {{{38/6}}} =  {{{19/3}}} = {{{6&1/3}}} miles 

To find the total distance, we use the improper fraction for
the distance at 38 mph 

Total distance = {{{30}}}{{{""+""}}}{{{19/3}}}{{{""=""}}}{{{90/3}}}{{{""+""}}}{{{19/3}}}{{{""=""}}}{{{109/3}}} or {{{36&1/3}}} miles.

 Total time = {{{1/2}}}{{{""+""}}}{{{1/6}}}{{{""=""}}}{{{3/6}}}{{{""+""}}}{{{1/6}}}{{{""=""}}}{{{4/6}}} or {{{2/3}}} hr.

Average Rate = Total Distance ÷ Total Time

We will use the improper fraction for the total miles  

Average Rate = {{{109/3}}}÷{{{2/3}}}{{{""=""}}}{{{109/3}}}{{{""*""}}}{{{3/2}}}{{{""=""}}}{{{109/cross(3)}}}{{{""*""}}}{{{cross(3)/2}}}{{{""=""}}}{{{109/2}}}{{{""=""}}}{{{54&1/2}}}mph.

Edwin</pre>