A man swims downstream 45 km and upstream 18 km taking 3 hours each time, what is the speed of the man in still water?  Answers.
A) 2  B) 8  C) 9  D) 10  E) 10.5

Rationale: "45 - - - 3 ds = 15 ? - - - - 1 18 - - - - 3 us = 6 ? - - - - 1 m = ? m = ( 15 + 6 ) / 2 = 10.5 answer : e"
Answer: E