Ritu can row downstream 20 km in 2 hours and upstream 4 km in 2 hours. Find her speed of rowing in still water and the speed of the current.

let the speed of ritu in still water be x km /hr and current be y km /hr

then , for downward , speed = x+y then , t = d/s => t = 20/ x+y => 20/ x+y =2

or , x+y = 10 ..............(1)

and for upstream = x-y then , t = d/s => t = 4/ x-y => x-y =2 .....................(2)

then from 1 and 2 we get

x+y +x-y = 10+2 => 2x =12 => x =6

then y = 10-6 =4

then speed in still water = 6 km/hr adn current = 4 km/hr

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