A man can row upstream at 25 kmph and downstream at 37 kmph, and then find the speed of the man in still water?  Answers:
A) 86  B) 67  C) 31  D) 15  E) 17

Rationale: "us = 25 ds = 37 m = ( 37 + 25 ) / 2 = 31 answer : c"
Answer: C