Question
If a boat travels with a speed of 12 km/hr in still water and the speed of stream is 3 km/hr, what would be the time taken (in hours) by boat to go 60 km downstream?
The correct answer is
4
Calculating Downstream Boat Travel Time
To find the time taken for the boat to travel 60 km downstream, we first need to determine the boat's speed when moving with the stream.
Boat Speed Downstream
When the boat travels downstream, its speed relative to the ground is the sum of its speed in still water and the speed of the stream.
- Speed of boat in still water = 12 km/hr
- Speed of stream = 3 km/hr
- Downstream Speed = Speed of boat + Speed of stream
- Downstream Speed = 12 km/hr + 3 km/hr = 15 km/hr
Time Calculation
The formula relating distance, speed, and time is: Time = Distance / Speed.
- Distance = 60 km
- Downstream Speed = 15 km/hr
- Time = $\frac{60 \text{ km}}{15 \text{ km/hr}}$
- Time = 4 hours
Therefore, the time taken by the boat to travel 60 km downstream is 4 hours.
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Important Questions from Boat and River
- A boat moves at a speed of 7 km/h in still water. The boat goes 40 km downstream and then 40 km upstream. It is observed that the total time taken for this journey is 560 minutes less than the time it would take if the speed of the stream were 2 km/h faster. What is the initial speed (in km/h) of the stream?
- A boat travels 120 km downstream in 6 hours and 120 km upstream in 10 hours. The speed of the current is 4 km/hr. What is the speed of the boat in still water?
- Ashok rows 43.5 kmph in still water. If the river is running at 14.5 kmph, it takes him 90 minutes to row to a place and back. How far is the place from the starting point? (In km)
- Aman can go downstream thrice as fast as he can go upstream between two specific points on a river. If the river flows at 8 kmph, what is the speed of the boat in still water (in kmph) ?
- A boat goes 288 km downstream in 32 hours and a distance of 217 km upstream in 31 hours. Find the speed of the water. (In kmph)
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