A motor boat whose speed in still water is 18km/h, takes 1 hour more to go to 24 km upstream than to return downstream to the same spot. Find the speed of the stram.
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Answered by
10
let speed of stream=x km/h
net speed of boat in upstream =(18-x) km/h
net speed of boat in downstream =(18+x) km/h
according to question
24/(18-x) -24/(18+x)=1
=> 24 { 2x/(324-x^2)}=1
=> 48x=324-x^2
=> x^2+48x-324=0
=>x=6,-54
but x=-54 isn't possible
so x=6
hence speed of stream =6 km/h
net speed of boat in upstream =(18-x) km/h
net speed of boat in downstream =(18+x) km/h
according to question
24/(18-x) -24/(18+x)=1
=> 24 { 2x/(324-x^2)}=1
=> 48x=324-x^2
=> x^2+48x-324=0
=>x=6,-54
but x=-54 isn't possible
so x=6
hence speed of stream =6 km/h
Answered by
1
Answer:
Let the speed of stream be x km / hr
For upstream = ( 18 - x ) km / hr
For downstream = ( 18 + x ) km / hr
A.T.Q.
24 / 18 - x - 24 / 18 + x = 1
48 x = 324 - x²
x² + 48 x - 324 = 0
( x + 54 ) ( x - 6 ) = 0
x = - 54 or x = 6
Since speed can't be negative .
Therefore , speed of the stream is 6 km / hr .
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