Answer:
The rate of water current = 6 mi / h
Step-by-step explanation:
Speed of the boat in still water = u = 18 mi / h
Let Speed of the current = v
Now downstream speed is given by = u + v
And upstream speed is given by = u - v
Now time taken to travel 4 miles in downstream = [tex]\frac{4}{u + v}[/tex] ----------------------(1)
And time taken to travel 2 miles in upstream = [tex]\frac{2}{u - v}[/tex] ----------------------------(2)
Now from the question equation (1) = equation (2)
⇒ [tex]\frac{4}{u + v}[/tex] = [tex]\frac{2}{u - v}[/tex]
⇒ 4 u - 4 v = 2 u + 2 v
⇒ 2 u = 6 v
⇒ u = 3 v
⇒ given that u = 18 mi / h
⇒ v = [tex]\frac{18}{3}[/tex]
⇒ v = 6 mi / h
Thus the rate of water current = 6 mi / h
