A runner passes the 5-mile mark at 1 o'clock and the 20-mile mark at 3 o'clock. What is the runner's average speed during this time period?

Answer 1

The normal assumption is that the race is local (say a local marathon), so:

Between 1 o'clock and 3 o'clock is 2 hours and in that time the distance covered is 20-5 = 15 miles.

So the average speed of the runner is 15 miles ÷ 2 hours = 7.5 mph.

... that all depends upon when and where the runner and the clocks happen to be.

for instance, if one clock is in Arizona and the other in New Mexico, Utah, Nevada, or California, it depends upon the time of year, because neither Arizona nor sonora Mexico use daylight saving time, but their adjacent states do.

those factors can change the answer substantially.

so, the difference between the clocks could be 1, 2 or 3 hours!!!

e.g., the runner goes 15, 7.5, or 5 mph.