A man takes 4 hours and 30 minutes to row a boat a distance of 18 km downstream, and 3 hours 30 minutes to row the boat a distance of 7 km upstream. Find the speed of the stream.
Answer & explanation
Correct answer: option 4
Upstream Speed = Speed of Boat – Speed of current
Downstream Speed = Speed of Boat + Speed of current
Let the speed of the boat = x and the speed of the stream = y
According to the question,
The distance traveled downstream is 18 km. We know that the time taken to cover this distance downstream is 4 hours and 30 minutes, which is 4.5 hours.
x + y = \(\frac{18}{4.5}\) = 4 --- (A)
The distance traveled upstream is 7 km. We know that the time taken to cover this distance upstream is 3 hours and 30 minutes, which is 3.5 hours.
x - y = \(\frac{7}{3.5}\) = 2 --- (B)
From equations, A and B
x = 3 and y = 1
So the speed of the stream = 1