A man who can swin at the rate of 2 `(km)/hr)`(in still river) crosses a river to a point exactly opposite on the other bank by swimming in a direction of `120^@` to the flow of the water in the river. The velocity of the water current in `(km)/(hr)` is

Options

A. 1
B. 2
C. `1//2`
D. `3//2`

Answer

A

Explanation

Let speed of current be u.
for net velocity of man to be
normal to river flow.
`2 sin 30^(@) =u`
or u=1 km/hr