Question

a motorboat whose speed is 20 kilometre per hour in still water takes 1 hour more to go for 48 km upstream then to return downstream to the same spot find the speed of the stream.

Answer 1

Let the speed of stream be x.
And upstream = 48/20-x
Downstream = 48/20+48
A/Q,

48/20-x + 48/20+48 = 1
48(20+x-20+x) = (400- x²)
48 (2x) = 400- x²
96x -400 + x²= 0
X²+96x-400= 0
X²+100x-4x -400=0
X(x+100)-4(x+100)=0
(X-4)(x+100)=0

Let (x-4)=0 as first term
x-4=0
x=4

Second term = (x+100)=0
x+100=0
x=-100

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