A rower whose speed is 4 km/hr in still water rows to a certain point upstream and back to the starting point in a river which flows at 2 km/hr. What is the rower's average speed (in km/hr) for the total journey?
Choose the correct answer: A) 6 B) 4 C) 9 D) 3 E) 2
time upstream = d / 2   time downstream = d / 6   total time = d/2 + d/6 = 2d/3   average speed = 2d / (2d/3) = 3 km/hr   The answer is 3.2  / (2 /3)= 
<gadget id="calculator">2  / (2 /3)</gadget>
<output>3</output>
3 km/hr   The answer is 3.
<result>D</result>
A rower whose speed is 4 km/hr in still water rows to a certain point upstream and back to the starting point in a river which flows at 2 km/hr. What is the rower's average speed (in km/hr) for the total journey?