Question

16. A boat travels 30 km upstream in the same amount of time it takes to travel 60 kmdownstream in the same river. If the speed of the river is 4 km/h, find the speed of the boat in still water.


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Answer 1

Answer:

V(upstream) = x + (–4) = x – 4 km/hr.

Similarly, relative velocity of boat going downstream = Speed of boat + Speed of river

⇒ V(downstream) = x + 4 km/hr.

Now, as the time taken is same so one can write it as:

Time taken in going upstream = Time taken in going downstream

⇒(Displacement/Velocity going upstream) = (Displacement/Velocity going downstream)

Since, Velocity = (Displacement/Time)

⇒[30/(x−4)]=[60/(x+4)]⇒[30/(x−4)]=[60/(x+4)]

⇒(x+4)/(x−4)=60/30⇒(x+4)/(x−4)=60/30

⇒(x+4)=2∗(x−4)⇒(x+4)=2∗(x−4)

⇒(x+4)=2x−8⇒(x+4)=2x−8

⇒4+8=2x−x⇒4+8=2x−x

⇒x=12km/hr.⇒x=12km/hr.

So, the speed of the boat in still water = x = 12 km/hr.

Step-by-step explanation:

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Answer 2

Answer:

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