Question

A boatman rows $1km$ in $5$ min along the stream and $6km$ in $1h$ against the stream. The speed of the stream is

• A. $3km/h$
• B. $6km/h$
• C. $10km/h$
• D. $12km/h$

Answer 1

The correct option is A $3km/h$

Let the speed of boat be x km/h and stream by y km/h

$1^{st}$ situation : -

$x+y=\frac{1}{\frac{5}{60}}=\frac{60}{5}=12$

$x+y=12...\left(1\right)$

$2^{nd}$ situation :-

$x-y=\frac{6}{1}$

$x-y=6...\left(2\right)$

subtract both equations

$2y=6$

$y=3$

speed of stream = 3 km/h