Question

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

Answer 1

hope you understand the solution

Answer 2

The “speed of the given stream” is 4km/hr.

Solution:

Now let us take the speed of the stream as x

Therefore, the speed of boat upstream is equal to $\frac{48}{20-x}$ and the speed of the boat downstream is $\frac{48}{20+x}.$

Now as to find the value of the speed of the stream we subtract the speed of downstream from upstream we get:

\frac{48}{20-x}-\frac{48}{20+x}=1

$48(2 x)=400-x^{2}$

$x^{2}+96 x-400=0$

$x(x+100)-4(x+100)$

x=4,-100    

Now as we can see that after solving the equation we get two values one is 4 and the other one is -100. Now the value of speed can never be negative therefore x = 4 km/hr is the correct value for the speed of the stream.