Question

a man can row 7.5 kmph in still water and he finds that it takes him twice as long to row up as to row down the river. find the rate of stream.

Answer 1

let speed of stream = s
speed to row up = (7.5 - s)
speed to row down = (7.5 + s)
if time spent is doubled than the speed must be half as they are inversely proportional
which means
2*(7.5 - s) = (7.5 + s)
after solving we get
s = 2.5 kmph. #answer...
hope so your doubts are clear if not you may reply

Answer 2

Answer:

Rate of the stream = 2.5 Km/hour

Step-by-step explanation:

Let the speed of stream be s Km/hour

⇒ Speed of the boat to row up = (7.5 - s)

and Speed of the boat to row down = (7.5 + s)

Now, It takes the man twice as long to row up as to row down the river

⇒ 2 × (7.5 - s) = (7.5 + s)

Solving the obtained equation, We get

⇒ 15 - 2s = 7.5 + s

⇒ 15 - 7.5 = s + 2s

⇒ 3s = 7.5

⇒ s = 2.5 km/hour

Hence, Rate of the stream = 2.5 Km/hour