A man can row upstream at 7 kmph and downstream at 33 kmph, and then find the speed of the man in still water?	Pick:
A) 11
B) 77
C) 30
D) 20
E) 34

Rationale: "us = 7 ds = 33 m = ( 33 + 7 ) / 2 = 20 answer : d"
Answer: D