Question

a boat goes 28km upstream and while returning downstream covered 25% more distance covered in upstream.if boat takes 4 1/2 hr more to cover upstream tham downstream.find the speed of current,if speed of boat in still water is 2 1/2 m/s?​

Answer 1

Step-by-step explanation:

Speed of the current = (5 / 9) m / sec = (5 / 9) * (3600 / 1000) km / hr = 2 km / hr.

Let, speed of the boat in still water = S km / hr.

75% of 28 kms = 21 kms.

Upstream speed = (S - 2) km / hr.

Downstream speed = (S + 2) km / hr.

{21 / (S - 2)} - {28 / (S + 2)} = 3

3 (S^2) - 12 = 21S + 42 - 28S + 56

3(S^2) + 7S - 110 = 0

3(S^2) + 22S - 15S - 110 = 0

(3S + 22) * (S - 5) = 0

Now, the value of S can't be negative.

So, S = 5.

Speed of boat in still water = 5 km / hr.

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