A boat can travel 10 km upstream in 2 hours. If the speed of the boat becomes half, then the return journey also takes the same time. What is the speed of water flow?
Explanation:
Let the speed of the boat be Vb and that of the stream be Vw.
Now, the time taken by the boat in going upstream = 10Vb-Vw = 2
⇒ Vb - Vw = 5 ... (i)
And the time taken by the boat in going downstream = 10Vb2+Vw = 2
⇒ Vb/2 + Vw = 5 ... (ii)
Adding (i) and (ii),
(3Vb)/2 = 10
Vb = 20/3
Vw = 5 - (10/3) = 5/3 kmph
The speed of the water flow is 5/3 kmph.
Hence, option (a).
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