A boat takes 48 min to go 12 km downstream and comes back in 1 hr 20 min. Find speed of boat in still water.

12 km/hr

Speed of boat in Downstream (X) = \(\frac{distance}{time}\) = \(\frac{12}{48}\) × 60 km/hr = 15 km/hr

Speed of boat in Upstream (Y)= \(\frac{distance}{time}\) = \(\frac{12}{80}\) × 60 km/hr = 9 km/hr

Speed of boat in still water = \(\frac{X + Y}{2}\) = \(\frac{15 + 9}{2}\) = 12 km/hr