Question

Q.56.
1. A boy rows a boat against a stream flowing at 2 kmph
for a distance of 9 km, and then turns round and rows _
back with the current. If the whole trip occupies 6
hours, find the boy's rowing speed in still water.
1) 4 kmph 2) 3 kmph
3) 2 kmph
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Answer 1

Step-by-step explanation:

ok I hope it help you friend

Answer 2

The correct option is 1) 4 kmph.

Step-by-step explanation:

Consider the provided information.

The stream flowing at 2 kmph let the speed of boat is x kmph.

As we know: $Time =\frac{Distance}{Speed}$

The distance is 9 km and total time is 6 hrs.

If boat against the stream then relative speed is x-2, if boat is in the direction of stream then the relative speed is x+2.

$\dfrac{9}{x-2}+\dfrac{9}{x+2}=6$

$\dfrac{9(x+2)+9(x-2)}{x^2-4}=6$

$9x+18+9x-18=6x^2-24$

$6x^2-18x-24=0$

$x^2-3x-4=0$

$x^2+x-4x-4=0$

$x(x+1)-4(x+1)=0$

$x=4\ or\ x=-1$

The value of x can't be a negative number.

Therefore,  the boy's rowing speed is 4 kmph in still water.

Hence, the correct option is 1) 4 kmph.

#Learn more

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