Question

A boat has speed of 18km /hr in still water. In a certain river it takes 1 hour more to go 24km/hr upstream what is the speed at which water is flowing in the river?​

Answer 1

Step-by-step explanation:

Given:

Speed of boat in still water = 18km/hr

Let speed of the stream = s

Speed of boat upstream = Speed of boat in still water - speed of stream = 18−s

Speed of boat down stream = Speed of boat in still water + speed of stream = 18+s

Time taken for upstream = Time taken to cover downstream + 1

⇒  $\frac{DISTANCE upstream}{SPEED upstream} =\frac{DISTANCE downstream}{SPEED downstream} +1$

⇒$\frac{24}{18-s} =\frac{24}{18+s} +1$

⇒$24(18+s)=24(18-s)+(18-s)(18+s)$

⇒$s^{2}+48s-324=0$

⇒$s^{2} + 54s-6s-324=0$

⇒$(s+54)(s-6)=0$

⇒$s=6,-54$

⇒$s$ ≠ $-54$

Thus, s=6km/hr, Speed of steam cannot be negative.

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