A man can row 48 km upstream and 56 km downstream in 12 hrs Also he can row 54 km upstream and 70 km...........

Quantitative Aptitude ( CCS) Boats and Streams

A man can row 48 km upstream and 56 km downstream in 12 hrs. Also, he can row 54 km upstream and 70 km downstream in 14 hrs. What is the speed of man in still water?

4 km/hr

10 km/hr

12 km/hr

15 km/hr

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Explanation:

Let upstream speed = x km/hr, downstream speed = y km/hr
So 48/x + 56/y = 12
And 54/x + 70/y = 14
Put 1/x = u, 1/y = v
So equations are 48u + 56v = 12 and 54u + 70v = 14
Solve the equations, u = 1/6, v = 1/14
So upstream speed = 6 km/hr, downstream speed = 14 km/hr
Speed of boat in still water = 1/2*(6+14)=10