A person can row at 9 kmph and still water. He takes 6 1/2 hours to row from A to B and back. What is the distance between A and B if the speed of the stream is 1 kmph? Choose the correct choice.
A) 60 km B) 87 km C) 89 km D) 29 km E) 20 km
Let the distance between A and B be x km.   Total time = x/(9 + 1) + x/(9 - 1) = 6.5   =&gt; x/10 + x/8 = 13/2 =&gt; (4x + 5x)/40 = 13/2 =&gt; x   = 29 km.   Answer:29 km
<result>D</result>
A person can row at 9 kmph and still water. He takes 6 1/2 hours to row from A to B and back. What is the distance between A and B if the speed of the stream is 1 kmph?