Pi Day!

Why is March 14 Pi Day? I dunno! At 1:59 pm today we set out to find out.


We used a string, a ruler, and three common objects shaped in circles.

First we wrapped the string around each circle, cut it so it was the same size as the circle, then straightened it back out and measured it. We wrote down our results in our handy dandy notebook under the title of "circumference".

Secondly we measured across each circle, and wrote that down too (we called these "diameters").

Thirdly, using a calculator we divided the circumference by the diameter for each circle and wrote down our answers (we called these results "pi").

Then we looked at our results. It still wasn't clear what "Pi Day" meant, but we started to see a pattern developing.


Here's what we had so far:
Pie pan circumference=30", diameter=9.25", pi=3.2432
Pumpkin can circumference=12.5", diamter=4", pi=3.125
Milk can circumference=9", diameter=2.8", pi=3.2143

Surprisingly, the final answers for pi were all almost the same, even though our circles had all been very different sizes.


Finally, we figured out the average of our three numbers for pi, by adding them up and then dividing by 3. The answer to that came to 3.19. When we looked up the REAL value for pi on the internet, we found it was 3.14 -- we were very close! We determined that if we had a way to take more accurate measurements of our circles, our number would probably have been even closer.

So now we know that no matter how big or small a circle is, the ratio of its circumference to its diameter will ALWAYS be 3.14.

Suddenly, it became clear why March 14 (3.14) is Pi Day! Bonus points to any cousins who can tell me why we started our pie experiment at 1:59.

And even bigger bonus points to anyone who can stop by and help us eat our pumpkin pi!