Pi Day is coming up on March 14. Get it? π = 3.14. March 14 =3/14. This year, 2015, makes Pi Day (3/14/15) all the cooler, because the first 5 digits of π are 3.1415. Next year gets its glory too, since π = 3.1416 if you obey rounding rules. It’s the little things that bring us joy in my family.
In the run-up to Pi Day, my 8-year-old twin daughters have been assigned π-related projects of their choosing in their Gifted and Talented class. M, ever the perfectionist, is still pondering her choices, but J has decided to calculate the volume of the sun. Along the way, J will learn how to calculate the volume of a sphere to teach her classmates.
It warmed my heart when, as J was excitedly telling a family friend all about her project, she said, “I already knew about pi, because Mom helped us discover it with coins and stuff. It’s the relationship between diameter and circumference of every circle.” I was especially happy to hear this 3 months after we did that exercise. Since it made such an impression on my girls, I thought I’d share the activity with the parents of mathematically minded children everywhere.
In December, we spent a day with dear friends, both physicists by training and IT professionals by vocation, who are expecting their second child and first daughter on Pi Day. My 8-year-olds wanted in on the joke, so I promised to explain it to them when we got home.
We measured all sorts of round things: coins, pot lids, coffee mugs, you name it. We used a piece of string around the edges to capture the circumferences and another piece of string across the middle to find the diameter. We then compared the scraps of string, finding that the circumferences were always just over three times as long as the diameters.
We then took it a step further, using a ruler to get a more precise measurement of each piece of string. Once we had our list of numbers, we punched them into the calculator, dividing each circumference by its diameter. We kept arriving at something close to 3.14.
I told my daughters that they had discovered a universal constant. Pi is a special, almost magical, number that just is. I told them that scientists used it to design rocket ships. I told them that builders used it to estimate their supply needs. I told them that they could even use it to calculate how much air is needed to fill a soccer ball.
To ice the cake, I had J and M put the word “pi” in the all-knowing Google search field. When even Google confirmed their calculations, they were so excited that they began to dance and all our lengths of string went flying.
Is pi for elementary students? I think kids are capable of understanding most concepts, given the chance. Let’s just keep the idea that math might be boring or hard to ourselves, shall we?
Please note that my daughters’ mathematical interests are atypical for their age. This activity is appropriate only for children who are comfortable with the basics of division. They certainly don’t need to know how to do long division, but they should understand that division is the breaking of things into equal parts, and that those parts need not be whole numbers.
Thinking about trying this activity with your children? Please let us know how it goes!