A boat can go $72 k m$ downstream in $4$ hours and $36 k m$ upstream in $3$ hours. Calculate the speed of stream.

7 k m / h r

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3 k m / h r

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12 k m / h r

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6 k m / h r

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Solution

The correct option is B $3 k m / h r$
It is given that boat can go $72$ km downstream in $4$ hours that is:

Downstream speed $= \frac{72}{4} = 18$ km/hr

Also, the boat can go $36$ km downstream in $3$ hours

Upstream speed $= \frac{36}{3} = 12$ km/hr

We know that Speed of the stream $= \frac{1}{2} (d o w n s t r e a m s p e e d - u p s t r e a m s p e e e d)$ km/hr

Speed of the stream $= \frac{1}{2} (18 - 12) = 3$ km/hr

Hence, the speed of the stream is $3$ km/hr.

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A boat can go 72km downstream in 4 hours and 36km upstream in 3 hours. Calculate the speed of stream.

A boat can go $72 k m$ downstream in $4$ hours and $36 k m$ upstream in $3$ hours. Calculate the speed of stream.