a 500gallon bathtub is being filled with water. 80 gallons of water are in the bathtub after 4min. How long will it take to fill the bathtub?
Assuming a constant rate of fill, the bathtub is filling at (80 gal)/(4 min)=20 gal/min. The time to get 500 gal is (500 gal)/(20 gal/min)=25 min