A boat travels 60 kilometers downstream and 20 kilometers upstream in 4 hours. The same boat travels 40 kilometers downstream and 40 kilometers upstream in 6 hours. What is the speed (in km/hr) of the stream?

Let speed of boat = $$x$$ km/hr and speed of stream = $$y$$ km/hr

Thus, downstream speed = $$(x+y)$$ km/hr and upstream speed = $$(x-y)$$ km/hr

Using, time = distance/speed

=> $$(\frac{60}{x+y})+(\frac{20}{x-y})=4$$

=> $$\frac{15}{x+y}+\frac{5}{x-y}=1$$ ---------------(i)

Similarly, $$(\frac{40}{x+y})+(\frac{40}{x-y})=6$$

=> $$\frac{1}{x+y}+\frac{1}{x-y}=\frac{3}{20}$$ ------------(ii)

Solving equations (i) and (ii), we get : $$x=24$$ and $$y=16$$

$$\therefore$$ Speed of stream = 16 km/hr

=> Ans - (B)