man can row upstream at 10 kmph and downstream at 20 kmph, and then find the speed of the man in still water?	Choose the most appropriate option.
A) 5	B) 20	C) 30	D) 25	E) 15

Rationale: us = 10 ds = 20 m = ( 10 + 20 ) / 2 = 15 answer : e
Answer: E