A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:
Choose the correct answer:
A) 2 km/hr B) 1 km/hr C) 4 km/hr D) 6 km/hr E) 5 km/hr
Explanation:   Assume that he moves 4 km downstream in x hours.   Then, speed downstream = distance/time = 4/x km/hr   Given that he can row 4 km with the stream in the same time as 3 km against the stream   i.e., speed upstream = 3/4 of speed downstream   =&gt; speed upstream = 3/x km/hr   He rows to a place 48 km distant and comes back in 14 hours   ⇒48/(4/x)+48/(3/x)=14   ⇒12x+16x=14   ⇒6x+8x=7   ⇒14x=7   ⇒x=1/2   Hence, speed downstream =4x=4(12) = 8 km/hr   speed upstream = 3x=3(12) = 6 km/hr   Now we can use the below formula to find the rate of the stream   Let the speed downstream be a km/hr and the speed upstream be b km/hr, then   Speed in still water = 1/2(a+b) km/hr   Rate of stream = 1/2(a−b) km/hr   Hence, rate of the stream = 1/2(8−6)= 1 km/hr   Answer: Option 1 km/hr
<result>B</result>
A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is: