Question

Guys, can you help me with this one?

Answer 1

The formula for average speed for a specific covered distance = (Total distance/Total time)

So, let us assume the distance from Paul's apartment to his parent's house be 'd' miles.

For the first trip, Time taken(t1) = Distance/Speed
=>t1 = d/60 hours

For the second trip, Time taken(t2) = Distance/Speed
=>t2 = d/80 hours

Also, as a result, the Total Distance covered becomes d+d = 2d

So, here we come,
Average speed = (d+d) / (t1 + t2)
=> 2d / (d/60 + d/80) miles oer hour
=>2d / (7d/240) miles per h
=> 2*240/7 miles per h
=>480/7 miles per h
=>68.5714.... miles per hour