Let speed of boat in still water = $$x$$ km/hr => Speed of current = $$y$$ km/hr Let distance travelled = $$d$$ km Acc. to ques, => $$2.2 (frac{d}{x + y}) = frac{d}{x - y}$$ => $$2.2x - 2.2y = x + y$$ => $$2.2x - x = y + 2.2y$$ => $$3x = 8y$$ -------------(i) Also, the man takes 2 hrs 30 mins in travelling 55 km downstream. => $$frac{55}{x + y} = 2 + frac{1}{2}$$ => $$frac{55}{x + y} = frac{5}{2}$$ => $$x + y = 22$$ Multiplying both sides by 8, and using eqn(i), we get : => $$8x + 3x = 22 imes 8$$ => $$x = frac{22 imes 8}{11} = 16$$ km/hr