Question

In a stream running at 2 kmph, a motorboat goes 6 km upstream and back again to the starting
point in 33 minutes. Find the speed of the motorboat in still water.

Answer 1

Let the speed of the motorboat in still water be x kmph.

Then, speed downstream = (x + 2) kmph.

Speed upstream = (x - 2) kmph.

:. 6/(x + 2) + 6/(x - 2) = 33/60 0r 11X2 –

240x – 44=0

11X2 – 242X + 2X –44 =0 or 11x(x – 22) + 2(x – 22) = 0

or (x-22)(11x+2)=0 or x=22.

:. Speed of motorboat in still water = 22 kmph.

Answer 2

Answer:

Speed of motorboat in still water = 22 kmph.

Step-by-step explanation:

As per the data given in the question,

we have,

Lets assume speed of the motorboat in still water be $x$ kmph.

So, speed downstream = $(x + 2)$ kmph.

Speed upstream = $(x - 2)$ kmph.

Distance travelled in one round = 6 km

As, time=distance/time

So, upstream time + downstream time = total time

$\frac{6}{(x + 2)}+ \frac{6}{(x - 2)} = \frac{33}{60}\\ 11\times2-240x - 44=011x^{2} -242x + 2x -44 =0 \\ 11x(x - 22) + 2(x - 22) = 0\\(x-22)(11x+2)=0$

ss, x=22 or x= -2/11. Since negative speed is not possible so,

Speed of motorboat in still water = 22 kmph.

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