Boats and Streams | Arithmetic aptitude | Discussion Page

The speed of a boat in still water is 10 km/hr. If it can travel 26 km downstream and 14 km upstream in the same time, the speed of the stream is :

A) 2 km/hr

B) 2.5 km/hr

C) 3 km/hr

D) 4 km/hr

E) 5 km/hr

Option C

Let the speed of the stream be $x$ km/hr. Then,

Speed downstream $=(10+x)$ km/hr, Speed upstream $=(10-x)$ km/hr.

$\frac{26}{(10 + x)}$ $=\frac{14}{( 10 - x )}$

$\Leftrightarrow 260 - 26x$ $=140 + 14x$

$\Leftrightarrow 40x=120$ $\Leftrightarrow x$ = 3 km/hr.

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