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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.

Posted by Yash Thadani 8 years, 1 month ago

CBSE > Class 08 > Mathematics

1 answers

Naveen Sharma 8 years, 1 month 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 = ${20\over x-4 }\space hour$

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

ATQ,

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

$=> 20x+ 80 = 30x - 120$

$=> 30x - 20x = 120 + 80$

$=> 10 x = 200$

=> x = 20

Speed of Boat in still water = 20 Km/h

3Thank You

ANSWER

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