Aship traveled 150 km with the current, and then turned around and traveled back, spending 5h and 30 min on its trip. find the speed of the current if the speed of the ship in still water is 55 km/hour.

150=(55-c)(5.5-t)

5.5-t=150/(55-c)

-t=(150-302.5+5.5c)/(55-c)

t=(152.5-5.5c)/(55-c)

150=(55+c)t   using t found about

150=(55+c)(152.5-5.5c)/(55-c)

8250-150c=8387.5-302.5c+152.5c-5.5c^2

5.5c^2=137.5

c^2=25

c=5

So the current is 5mph.