Question 1088688
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<pre>
The average speed is, by the definition, the total distance divided by total time.


The total distance is  {{{8*(1/4) + 4*(3/4)}}} = 2 + 3 = 5 miles.


    <U>Exlanation</U>. {{{1/4}}} = 15 minutes = 1/4 of an hour.

                {{{3/4}}} = 45 minutes = 3/4 of an hour.


The total time is 15 minutes + 45 minutes = 1 hour.


Hence, the average speed is  {{{5_miles/1_hour}}} = 5 mph.
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Solved.