A man can row a boat in still water at the rate of 12 km/hr. He finds that it takes him thrice as much times to row upstream than downstream. The speed of the current is :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 6 km/hr
Speed of man in still water = $12\, km/hr$
Speed of current = $x\, km/hr$
Downstream speed = $12+x\,km/hr$
Upstream speed = $12-x\,km/hr$
and,
$\frac{d}{12-x}=3×\frac{d}{12+x}$ [d = Distance]
$⇒12+x=36-3x$
$⇒4x=24$
$⇒x=6\,km/hr$