Boats And Streams
Some terminologies-
Downstream move- A boat is said to be moving in downstream if it is moving in the direction of the flow of water.
Upstream move- A boat is said to be moving in upstream if it is moving in the opposite direction of the flow of water.
Still water- There is no motion in the water.
If the speed of a boat in still water is x meter/second and speed of the stream is y meter/second, then
Speed of the boat with downstream= (x+y) meter/second
Note- In the downstream speed of water helps because the direction of the boat and water are the same.
Speed of the boat with upstream=(x-y) meter/second
Note-In downstream speed of water resists because the direction of the boat and water are in the opposite direction.
Again, Let the speed of the boat in downstream is a, and in upstream is b
then, we have
x+y=a ………..(1)
x-y=b ………..(2)
After solving both equations, we get
x=(a+b)/2
and y=(a-b)/2
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Question- A boat can cross a river at the upstream speed of 1 km/h and downstream speed of 3 km/h what is the speed of boat in still water and rate of the stream?
Solution-
Here a=3 and b=1
then we get, the speed of the boat in still water x=(3+1)/2=2 km/h
and, rate of the current y=(3-1)/2=1 km/h
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