Kids and Popcorn Tell Volumes

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Even parents who experienced math phobia when they were young can now spur their own kids to love math: Show them the world through a lens that reveals the fun of mathematics. When families have time together, that's a great time to play games and do activities that not only entertain, but also have mathematics at their heart.

Mathematics is entertaining? OK, try this with the kids, even those about four or five years old. See if it's fun.

• Take two pieces of 8.5 by 11-inch paper.
• Hold one piece on the long side and loosely roll it into a tall cylinder until the edges overlap just enough to stick a bit of tape on to hold it together.
• Hold the other piece of paper on the short side and loosely roll it into a tall cylinder until the edges overlap just enough to stick a bit of tape on to hold it together.
• Pop some popcorn.
  Ask the Kids to Estimate: Which cylinder will hold more popcorn? Why do you think so? Let's see.
• Put the tall cylinder into the short cylinder. Fill the tall cylinder to the top with popcorn.
• Slowly remove the tall cylinder so that the popcorn spills into the short cylinder.
  Now what do the kids think?

The activity shows that the short cylinder holds more than the tall cylinder. In other words, the short cylinder has a larger volume. Now roll the short cylinder tighter and see what happens. Let the kids play with rolling the cylinders tighter and looser, inserting one into the other, filling with popcorn, withdrawing, and seeing what happens. Does the diameter (how wide the cylinder is) make a difference? Can they figure out a way to make both cylinders hold the same amount of popcorn? Cylinder, volume, and diameter are all labels used in mathematics; use these words with the kids, and point out that what they're doing is mathematics.

This activity is adapted from one on the Web site Figure This! Math Challenges for Families http://www.figurethis.org/. The site, sponsored in part by a grant from the U.S. Department of Education and the National Science Foundation, is geared for parents and kids in grades 6-8. With kids in that age group, if you feel comfortable, you might go further to talk about how to find the volume of each cylinder (the volume is the area of the base times the height. In this activity, the base is circular). The site has answers and how to find them. If you feel uncomfortable, and the kids are up to it, ask them if they can show you how to work this through. After all, teaching is a very effective learning strategy.

This column by Karen Lytle Blaha is provided as a public service by the Northwest Regional Educational Laboratory, a nonprofit institution working with schools and communities in Alaska, Idaho, Montana, Oregon, and Washington.