Math, asked by khushi62, 1 year ago

a boat travels 20km upstream in a river in the same period of time as it takes to travel 30 km downstream . if the rate of the stream is 4 km/hr , find the speed of the boat in still water

Answers

Answered by TooFree
44

Let the speed of boat in still water be x


Upstream:

Speed = (x - 40) km/h

Distance = 20 km

Time = Distance ÷ Speed

Time = 20 / ( x - 40)


Downstream:

Speed = (x + 40)

Distance = 30 km

Time = 30 / (x + 40)


Since both the timing are the same:

20 / ( x - 40) = 30 / (x + 40)

20(x + 40) = 30(x - 40)

20x + 80 = 30x - 120

10x = 200

x = 20 km/h


Answer: The speed of the boat in still water is 20 km/h

Answered by sanchishethia4
3

Answer:

Let the speed of boat in still water be x.

Step-by-step explanation:

Distance = 20 km

Time = Distance ÷ Speed

Time = 20 / ( x - 40)

Downstream:

Speed = (x + 40)

Distance = 30 km

Time = 30 / (x + 40)

Since both the timing are the same:

20 / ( x - 40) = 30 / (x + 40)

20(x + 40) = 30(x - 40)

20x + 80 = 30x - 120

10x = 200

x = 20 km/h

Answer: The speed of the boat in still water is 20 km/h

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