This Instructional Activity is a part of the Lesson 3, Unit 5, Grade 8. Water flows from a faucet into a bathtub at the constant rate of gallons of water pouring out every minutes. The bathtub is initially empty, and its plug is in. Determine the rule that describes the volume of water in the tub as a function of time. If the tub can hold the given number of gallons of water, how long will it take to fill the tub?