If a boat can row upstream at 12 km/hr, and downstream at 20 km/hr, then the speed (in km/hr) of the stream and the speed (in km/hr) of the boat in still water are respectively :

4, 16

The correct answer is Option (1) → 4, 16

Speed of boat in still water = x km/hr

Speed of stream = y km/hr

Upstream speed = $x-y=12km/hr$   ....(1)

Downstream speed = $x+y=20km/hr$   ....(2)

from (1) and (2)

$(x+y)+(x-y)=32$

$2x=32$

$x=16km/hr,y=4km/hr$