Question

Q. A man rows at the rate of 12 kmph in still water. It takes him 4 hr 16 min to row to a
place 24 km away & back. What is the speed of water?
A. 3 kmph
B. 2.5 kmph C. 2 Kmph
D. 1.5 kmph​

Answer 1

Given info : A man rows at the rate of 12 kmph in still water. It takes him 4 hr 16 min to row to a

place 24 km away & back.

To find : the speed of water

solution : let the speed of water is x km/h.

a/c to question,

man takes 4 hr 16 min to row to a

place 24 km away & back.

i.e., 24/(x + 12) + 24/(12 - x) = 4 hr 16 min

⇒24[ 1/(x + 12) + 1/(12 - x)] = 4 + 16/60 = 256/60

⇒24[(12 - x + 12 + x)/(12² - x²)] = 64/15

⇒576/(144 - x²) = 64/15

⇒576 × 15/64 = 144 - x²

⇒135 - 144 = - x²

⇒x² = 9 = 3²

⇒x = 3

therefore the speed of water is 3 km/h.