An ambulance travels 10 miles at a speed of 75 miles per hour. How fast must the ambulance travel on the trip if the round-trip travel time is to be 20 minutes?

On the forward trip,

The ambulance travels,

75 miles in 60 mintues

10 miles in 60*10/75 minutes

                = 8 minutes

Now, to complete the round trip in 20 minutes, the ambulance must travel back to the first place in (20-8) mintues

                                           = 12 minutes

Now,

On the reverse trip, the ambulance,

in 12 minutes travels 10 miles

thus, in 60 minutes travels 10*60/12

                                    &nbs