A boat takes 11 hours to cover distance of 180 KM downstream while in H20,still takes 8 hrs.find time taken to cover a distance of 72km upstream?

Let the speed of the boat in still water be x km/hr and the speed of the stream be y km/hr.

Downstream speed = (x + y) km/hr
Upstream speed = (x - y) km/hr

Given that the boat takes 11 hours to cover 180 km downstream:
180 = 11(x + y)
x + y = 180/11

Given that the boat takes 8 hours to cover 180 km downstream:
180 = 8(x - y)
x - y = 180/8

Solving the above two equations, we get:
x = 25 km/hr
y = 5 km/hr

Now, to find the time taken to cover a distance of 72 km upstream:
72 = t(25 - 5)
72 = 20t
t = 72/20
t = 3.6 hours

Therefore, it will take 3.6 hours to cover a distance of 72 km upstream.