Boats and Streams | Arithmetic aptitude | Discussion Page

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

A) 1 : 2

B) 3 : 1

C) 2 : 1

D) 1 : 3

E) 2 : 3

Option B

Let the speed of boat in still water be $=x$ km/hr and that of current $=y$ km/hr

Rate upstream $=(x-y)$ km/hr and Rate downstream $=(x+y)$ km/hr

Let distance covered in each case be $d$ km

$\frac{2d}{( x+y )}$ $=\frac{d}{( x-y )}$

$\Rightarrow 2x-2y$ $=x+y$

$\Rightarrow x=3y$ $\Rightarrow\frac{x}{y}$ $=\frac{3}{1}$ = 3 : 1.

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