You've heard the phrases "a quantity that varies" and a quantity that stays constant" in this lesson. Describe what they mean in your own words. If possible given an example of a situation that has a quantity that varies and a quantity that stays constant. Sentence Frames to Use: 1. It makes sense to use only numbers when. . .and it makes sense to use letters when. . . 2. "A quantity that varies" means . . .and "a quantity that stays constant" means. . .