A motor boat can travel 30 km upstream and23 km downstream in 7 hours. It can travel 21 km upstream and return in 5 hours. Find the speed of the boat in still water and the speed off the stream.
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Let the speed of boat be Xkm/h
And speed of stream be Y km/h
Then the speed of boat in upstream mode
(X-Y) KM/h
And in down stream mode speed of boat be
(X+Y)
7h=30/x+y+23/x-y. . . . . (1)
Again in a/q to question
5h=21/X+y+21/X-y. . . . . (2)
Now from (1)and(2) equation elimination method apply(1)multiplying by7and (2)multiplying by(10)
Also you can let that 1/x+y=m
And 1/x-y=n
Then equation become easy
After that substitution method apply for second speed.
I hope you can do it, easily.
And speed of stream be Y km/h
Then the speed of boat in upstream mode
(X-Y) KM/h
And in down stream mode speed of boat be
(X+Y)
7h=30/x+y+23/x-y. . . . . (1)
Again in a/q to question
5h=21/X+y+21/X-y. . . . . (2)
Now from (1)and(2) equation elimination method apply(1)multiplying by7and (2)multiplying by(10)
Also you can let that 1/x+y=m
And 1/x-y=n
Then equation become easy
After that substitution method apply for second speed.
I hope you can do it, easily.
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