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Question

Rohit can row downstream 32 km in 4 hours and upstream 4km in 1 hour. Find his speed in still water and the speed of the current.


A

6 km/hr, 2 km/hr

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B

4 km/hr, 4 km/hr

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C

20 km/hr, 4 km/hr

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D

4 km/hr, 2 km/hr

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Solution

The correct option is A

6 km/hr, 2 km/hr


Let speed of Rohit rowing in still water = x km/hr
and speed of current = y km/hr. Then,
Speed downstream = (x + y) km/hr
Speed upstream = (x - y) km / hr
We know that,
Time=DistanceSpeed

4=32x+y and 1=4xy

x+y=8 (1)
xy=4 (2)
On adding (1) and (2), we get
2x = 12
x = 6
On substituiting x = 6 in (1), we get
6 + y = 8
y = 2
The rowing speed in still water is 6 km/hr and the speed of current is 2 km/hr.


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