A man can cross 10 miles distance of a river in favor of the stream in 2 hours . He can come back against the stream along the same way in 5 hours . What is the average speed, in miles per hour, for the entire trip ?
A
20/7
B
10/7
C
7/10
D
7/20
Correct Answer: 20/7
Total distance = 10 + 10 = 20 miles Total time required = 5 + 2 = 7 hours Average speed = 20/7 miles per hour