Question

Two groups went hiking, leaving at the same time and arriving back at the same time. While one group moved away at the speed 6 mph and then moved back at the speed 4 mph, the other group moved all the way with the same speed. What was the speed of this second group, if both groups covered the same total distance, 24 miles?

Answer 1

This uses the formula d = r * t
First group
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This group determines the time to be used by both groups.
t = d/r
t = 24 / 6
t = 4 hours hours going there.

t = 24 / 4
t = 6 hours 
Total time taken is 6 hours + 4 hours = 10 hours.

Group two
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t = 10 hours.
d = 48 miles (remember, they have to come back).
r = 48 miles / 10 hours
r = 4.8 miles / hour
For humans, that actually is quite quick.