Question

A person can row 20 km downstream in 2h and 4km upstream in 2h find s speed in water and also of the current

Answer 1

let the speed of person 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   and current = 4 km/hr