A man swims downstream 45 km and upstream 25 km taking 5 hours each time, what is the speed of the man in still water?	Pick one
A) 17  B) 24  C) 7  D) 24  E) 20

Rationale: "45 - - - 5 ds = 9 ? - - - - 1 25 - - - 5 us = 5 ? - - - - 1 m = ? m = ( 9 + 5 ) / 2 = 14 / 2 = 7 answer : c"
Answer: C