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Answer:

A steamer goes downstream. The distance between the two ports is 180 km.

Solution:

Let the speed of the streamer be ‘x’ and Distance be ‘D’

Given the speed of the stream is 1 km/hr.

Thus the downstream speed is given by ‘(x+1)’km/hr and the upstream speed is given by (x-1) km/hr.

Given that time taken to travel downstream is 9 hr

Therefore downstream distance = 9(x+1) …………..(Equation 1)

Again it is given that time taken to travel upstream is 10 hour.

Therefore upstream distance = 10(x-1)  ……………(Equation 2)

Since distance is same in both cases, we equate the upstream distance and downstream distance.

9(x+1) = 10(x-1)

9x + 9 = 10x - 10

9 + 10=10x - 9x

x = 19

Now substituting the value of "x" in any of the equation 1 or 2, we get

D = 10(19-1)     [Substituting the value of x in Equation 2]

D = 190-10  = 180

Thus the distance between two ports is 180 cm