Question

A boat which has a speed of `5 km// hr ` in steel water crosses a river of width ` 1 km` along the shortest possible path in `15 minutes`. The velocity of the river water in ` km// hr` is
A. `1`
B. `3`
C. `4`
D. `sqrt(41)`

Answer 1

Correct Answer - B
`V_(R ) = (1Km)/((1)/(4)h) = 4Km//h`
`V_(r) = sqrt(u_(B)^(2) -V_(R)^(2))`
`V_(r) = sqrt(5^(2)-4^(2)) = 3Km//h`