Question

Pls answer . I need it quickly

Answer 1

Let the speed of the stream be = u kmph

let the speed of the boat be = v kmph

speed upstream will be = v - u  kmph

speed downstream will be =  v + u  kmph

30 km  upstream in time duration  =   30 / (v - u)  hrs

44 km  down stream in time duration  =  44 / (v + u)  hrs

      44 / (v + u)  + 30 / (v -u)  = 10 hrs     --- (1)

Similarly,

     40 /(v - u)  + 55 / (v +u)  = 13 hrs         Multiply with 3/4:  

     30/(v-u) + 165 / 4(v+u) =    39/4        --- (2)  

Now (1) - (2)  =>    [44 - 165/4] / (v+u) = 10 - 39/4 = 1/4

                  =>     v + u = 11      --- (3)

Substitute this in (1) to get:  

            44/11 + 30/(v-u) = 10

          =>  v - u = 30/6 = 5      --- (4)

Solving  (3) and (4) ,  we get :  v = 8 kmph    and  u = 3 kmph