Question

The ratio of speed of a boat in still

water to speed of the current is 10 : 1. If

ratio of the time taken by the boat to

travel D km downstream to the time

taken to travel (D – 45) km upstream is

3 : 2. Find the value of D.​

Answer 1

Answer:

D = 99

Step-by-step explanation:

Let ratio of speed of a boat in still water to speed of the current is 10x : x,

then

     D/(10 + 1)x                   3

 ⇒  --------------------    =      ----

       D-45/ (10 - 1)x              2  

             D/(11)x                   3

  ⇒         -----------------     = ------

            D - 45 / (9)x           2

      ⇒  D/(11)x  X    (9)x/ D - 45  = 3/2

Cancelling (X) ,we get

       ⇒ D / (11)   X   9  / D - 45   = 3/2

      ⇒9D / 11 ( D - 45) = 3/2

      ⇒9D / 11D - 495 = 3/2

BY Cross Multiplication,

      ⇒ 2 (9D) / 3 (11D - 495) = 0

      ⇒18 D / 33D - 1485 = 0

      ⇒ 18D = 33D - 1485

      ⇒ 18D - 33D = - 1485

       ⇒ - 15D = - 1485

cancelling the sign( - ),

       ⇒ 15D = 1485

       ⇒D = 1485/15

        ⇒D = 99