This question involves the concepts of average speed, distance, and time.
The average speed of the family is "2.5 mi/hr".
The average speed is defined as the ratio of the total distance covered with the total time taken to cover it.
[tex]v=\frac{s}{t}[/tex]
where,
Therefore,
[tex]v=\frac{2.5\ mi}{1\ hr}[/tex]
v = 2.5 mi/hr
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