A motor boat covers 36 km downstream and 24 km upstream. If the boat takes 6 hours to cover each distance, then the speed of the motor boat in still water is,
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 5 km/hr
let the speed of the boat be $x$ km/hr
the speed of the stream be $y$ km/hr
Downstream speed = $\frac{36}{x+y}=6$
Upstream speed = $\frac{36}{x-y}=6$
$⇒x+y=6$ ...(1)
$x-y=4$ ...(2)
Add (1) and (2)
$2x=10$
$x=5\, km/hr$