試題詳解

10. A man launches a boat at a bridge and rows upstream a distance of 1 km where he drops a bottle in the water. He then continues to row upstream for an additional 10 min. At that point, he turns around and rows downstream, arriving at the bridge at the same time as the bottle. What is the speed of the water in the river? Assume that the man rows at the same speed relative to the water at all times.
(A) 0.83 m/sec
(B) 0.79 m/sec
(C) 1.20 m/sec
(D) 1.50 m/sec
(E) 0.90 m/sec