The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hours 30 minutes. Find the speed of the stream.

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Solution

Let the speed of the stream be $\frac{x k m}{h r}$ .
∴ Speed of the boat downstream = $\frac{(15 + x) k m}{h r}$
Speed of the boat upstream = $\frac{(15 - x) k m}{h r}$
$T i m e space t a k e n space t o space g o space 30 space k m space d o w n s t r e a m space equals fraction numerator 30 over denominator 15 plus x end fraction h r T i m e space t a k e n space t o space c o m e space b a c k equals fraction numerator 30 over denominator 15 minus x end fraction h r F r o m space t h e space g i v e n space i n f o r m a t i o n fraction numerator 30 over denominator 15 plus x end fraction plus fraction numerator 30 over denominator 15 minus x end fraction equals 4 30 over 60 fraction numerator 30 over denominator 15 plus x end fraction plus fraction numerator 30 over denominator 15 minus x end fraction equals 9 over 2 fraction numerator 450 minus 30 x plus 450 plus 30 x over denominator left parenthesis 15 plus x right parenthesis left parenthesis 15 minus x right parenthesis end fraction equals 9 over 2 fraction numerator 900 over denominator 225 minus x squared end fraction equals 9 over 2 fraction numerator 100 over denominator 225 minus x squared end fraction equals 1 half 225 minus x squared equals 200 x squared equals 25 x equals plus-or-minus 5 B u t space x space c a n n o t space b e space n e g a t i v e space comma s o space x equals 5 T h u s space t h e space s p e e d space o f space t h e space s t r e a m space i s space 5 space k m divided by h r$

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15

km/hr. It goes

30

km upstream and return downstream to the original point in

4

hrs

30

minutes. Find the speed of the stream(in km/hr).

Q. The speed of a boat in still water is

15

km/hr. It can go

30

km upstream and return downstream to the original point in

4

hrs

30

min. The speed of the stream is:

A boat can go 20 km upstream and 30 km downstream in 3 hrs. It can go 20 downstream and 10km upstream in 1 hrs 40 min . Find the speed of the boat in still water and speed of the stream.

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The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hours 30 minutes. Find the speed of the stream.

Let the speed of the stream be xkmhr. ∴ Speed of the boat downstream = (15+x)kmhr Speed of the boat upstream = (15–x)kmhr