Answer:
Doug's average speed is 7 miles per hour.
Step-by-step explanation:
Average speed is defined as ratio of total distance to the total time taken to cover the total distance.
Distance covered by Doug ,D=[tex]3\frac{1}{2} miles=\frac{7}{2} miles[/tex]
Time taken to cover the distance D = T= [tex]\frac{1}{2} hour[/tex]
Average speed :
[tex]=\frac{D}{T}=\frac{\frac{7}{2} miles}{\frac{1}{2} hour}=7 miles/hour[/tex]
Doug's average speed is 7 miles per hour.