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- Identify upstream or downstream.
- Apply the correct effective speed.
- Use distance/time relation.
Correct Answer: D
Correct Answer: D
Method / Topic: Boats and Streams
The answer uses the correct effective speed of the boat.
Short Explanation
Detailed Explanation
Correct Answer: D
Method / Topic: Boats and Streams
For upstream travel, subtract the speed of the stream from the speed of the boat in still water. Then use Time = Distance / Speed.
Speed of boat in still water = 15 km/h.
Speed of stream = 5 km/h.
Upstream speed = 15 - 5 = 10 km/h.
Distance = 60 km.
Time = 60 / 10 = 6 hours.
CHECK:
At 10 km/h, the boat covers 10 × 6 = 60 km in 6 hours. Hence the
Do not add the stream speed in an upstream
Therefore, the boat will take 6 hours to cover 60 km upstream.
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Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Shortcut used, common trap, and the fastest solving route
- Identify upstream or downstream.
- Apply the correct effective speed.
- Use distance/time relation.
A boat can travel at 15 km/h in still water. If the speed of the stream is 5 km/h, how long will it take to cover 60 km upstream?
Explanation
Correct Answer: D
Method / Topic: Boats and Streams
The answer uses the correct effective speed of the boat.
Short Explanation
Detailed Explanation
Correct Answer: D
Method / Topic: Boats and Streams
For upstream travel, subtract the speed of the stream from the speed of the boat in still water. Then use Time = Distance / Speed.
Speed of boat in still water = 15 km/h.
Speed of stream = 5 km/h.
Upstream speed = 15 - 5 = 10 km/h.
Distance = 60 km.
Time = 60 / 10 = 6 hours.
CHECK:
At 10 km/h, the boat covers 10 × 6 = 60 km in 6 hours. Hence the
Do not add the stream speed in an upstream
Therefore, the boat will take 6 hours to cover 60 km upstream.
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