Math Inquiry: How Many Cups in a Gallon?

We have been experimenting with capacity this week.  We started off by discovering how many cups are in a gallon.  Before our experiment, we made a prediction and collected our prediction data on a line plot. Then we came up with a plan for how we were going to go about this experiment.  The class decided to fill some gallon milk jugs with water and then use our measuring cups to pour the water into and count how many cups with got out of the gallon.  Then we set out to test our predictions!  Check out our pictures below and the video in which Manuel explains our process!

After experimenting we found that we came up with many different numbers.  Some groups found 13 cups in a gallon, some 18, some 20.  What could account for such different numbers?  Perhaps our gallon jugs were filled to different levels.  Or maybe we didn't fill our measuring cups exactly.  In the end, we found out that 1 gallon is equal to 16 cups.  And because we constructed this idea through hands-on experimentation, this is an idea we aren't likely to forget!