Question
Download Solution PDFThe speed of the stream is 4 km/h. The time taken by a boat to cover a certain distance upstream is equal to 2.5 of the time taken by it to cover the same distance downstream. What is the speed (in km/h) of the boat in still water?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
The speed of the stream is 4 km/h.
The time taken by a boat to cover a certain distance upstream is equal to 2.5 of the time taken by it to cover the same distance downstream.
Concept used:
Distance = Speed × Time
While rowing upstream, the upstream speed is the difference between the speed of the boat in still water and the speed of the flow.
While rowing downstream, the downstream speed is the addition of the speed of the boat in still water and the speed of the flow.
Calculation:
Let the speed of the boat in the still water be Q km/h and the distance be D km.
Upstream speed = (Q - 4) km/h
Downstream speed = (Q + 4) km/h
According to the question,
D/(Q + 4) × 2.5 = D/(Q - 4)
⇒ 2.5Q - 10 = Q + 4
⇒ 1.5Q = 14
⇒ Q = 14/1.5
⇒ Q = \(9\frac{1}{3}\)
∴ The speed of the boat in the still water is \(9\frac{1}{3}\) km/h.
Last updated on May 9, 2025
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