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A man crosses a 320m wide river perpendi...

A man crosses a `320m` wide river perpendicular to the current in `4` min. If in still water he can swim with a speed `5//3` times that of the current, then the speed of the current, in `m//min` is

A

`30`

B

`40`

C

`50`

D

`60`

Text Solution

Verified by Experts

The correct Answer is:
D
`t=d/(sqrt(v^(2)-u^(2))),v=5/3 u`
`4=320/(sqrt((5/3u)^(2)-u^(2)))=320/(4/3u)`
`u=60m//min`
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