Question 16

A boat covers 12 km upstream in 4 hours and can cover the same distance downstream in 3 hours. What is the speed (in km/hr) of the boat in still water?

Solution

Let speed of boat in still water = $$x$$ km/hr and speed of current = $$y$$ km/hr

Speed upstream = $$(x-y)$$ km/hr

Using, speed = distance/time

=> $$x-y=\frac{12}{4}=3$$ ----------------(i)

Similarly, downstream speed = $$x+y=\frac{12}{3}=4$$ ---------------(ii)

Adding equations (i) and (ii), we get : $$2x=3+4=7$$

=> $$x=\frac{7}{2}=3.5$$ km/hr

=> Ans - (A)

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