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A Boat takes 3 hours to …

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A Boat takes 3 hours to go 45 km downstream and IT returns in 9 hours find the speed of stream and that a boat in still water

  • 1 answers

Naveen Sharma 6 years, 11 months ago

Ans. Let Speed of boat in still water = x km/h

Speed of stream = y km/h

According to question, 

Case 1 Downstream :

Time taken = 3 hours

total distance = 45 km 

Speed of  boat downstream = x + y 

So, {tex}{45\over 3} = x+y{/tex}

=> x+y = 15    ............. (1)

Case 2 Upstream : 

Time taken = 9 hours

total distance = 45 km 

Speed of  boat upstream = x - y 

So, {tex}{45\over 9} = x-y{/tex}

=> x -  y = 5   ..............(2)

Adding (1) and (2) we get

=> 2x = 20 

x = 10 

From (2). 10 - y =  5 

=> y = 5 

So speed of boat in still water = 10 Km/h

Speed of stream = 5 Km/h

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