Given, the speed in the first trip, S1=40 miles/h.
The speed in the return trip, S2=50 miles/h.
The distance is the same for both trips.
When the distance is same, the average speed of the drive is,
Given, the time taken for entire trip is t=9 h.
Now, the distance travelled both ways to park is,
Hence, the distance travelled one way to the park is,
Therefore, the distance travelled one way to the park is 200 miles.