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A boat travels 20 km upstream …

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A boat travels 20 km upstream in a river in the same period of time as it takes to travel 30 km downstream if the rate of the stream is 4 km/hr find the speed of boat in still water. 

  • 1 answers

Naveen Sharma 6 years, 11 months ago

Ans. Let the speed of boat in still water = x Km/h

rate of stream = 4 Km/h

 So, Speed of Boat downstream = (x+4) Km/h

Speed of Boat upstream = (x-3) Km/h

 Time Taken to travel 20 Km Upstream = {tex}{20\over x-4 }\space hour {/tex}

Time Taken to travel 30 Km Downstream = {tex}{30\over x+4} \space hour{/tex}

ATQ,

{tex}=> {20\over x-4} = {30\over x+4}{/tex}

 {tex}=> 20x+ 80 = 30x - 120{/tex}

 {tex}=> 30x - 20x = 120 + 80 {/tex}

{tex}=> 10 x = 200 {/tex}

=> x = 20 

Speed of Boat in still water = 20 Km/h

 

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