Discussion

A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between the rate in still water and rate of current?

Answer: B

Let the speed of the boat in still water be 4 km/hr and speed of the current be u km/hr.

Rate downstream = (u + v) km/hr.

Rate upstream = (u- v)km/hr

Let the distance covered in each case be x km.

Then 2x/(u + v) = x / (u - v)

=> 2 (u - v) = ( u + v)

=> u =3v

=> u/v =3/1

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