A rower whose speed is 2.5 km/hr in still water rows to a certain point upstream and back to the starting point in a river which flows at 0.5 km/hr. What is the rower's average speed (in km/hr) for the total journey?	Choose the correct choice from the following options.
A) 2.2  B) 2.3  C) 2.4  D) 2.5  E) 2.6

Rationale: time upstream = d / 2 time downstream = d / 3 total time = d / 2 + d / 3 = 5 d / 6 average speed = 2 d / ( 5 d / 6 ) = 2.4 km / hr the answer is c .
Answer: C