Question

Dear Mitch,

At our school, this Friday, March 14^{th}, is called "Pi Day" and all the math classes do something with circles.

I know that they call it "Pi Day" because of its date which is 3-14, but I don't really know much about Pi itself, so could you tell me?

And how did they ever come up with such an odd number?

Sincerely,

Matthew

Marion, OH

Answer

Dear Matthew,

Sure!

First of all, before getting to what is 'right' about "pi", it is a good idea to know which commonly held beliefs are wrong.

First, Pi is NOT infinite. In fact, it is less than the number 4! (It's between 3 and 4).

Second, even though the constant Pi has an exotic reputation, it is something you can actually come up with on your own and check for yourself with a simple tape measure.

How?

Like this:

Set up a chart with 3 columns:

The first column is for the **circumference** of various circular objects in your classroom (or in your home) that you will measure,

The second column is for the **diameter** of those circular objects, and ...

The third column is for the amount your calculations show the **Pi** ingredient of the equation should equal, based on the formula c = (pi) (D).

The circumference is easy to determine by wrapping a tape measure around the outside of a cylinder or circle, such as a roll of paper towels or a soup bowl, though you may need occasional bits of scotch tape to hold the tape measure in place and to assure that it is parallel with the top edge of whatever you are measuring (for accuracy).

The diameter is easy to determine by holding out an expanse of the tape measure and sliding it around on the surface of the rim of the object; whenever the measurement across is largest, you have the diameter!

You asked: "How'd they ever come up with such an odd number?"

Well, I think you too will note an oddity in your results if you are careful to avoid too much "rounding".

'Your' pi should resemble 'their' pi. If not, try again.

Finally, if you like odd coincidences, here's one: Pi Day, 3/14 just happens to have been the birthday of ... Albert Einstein. Yup, on this day in the year 1879 the boy was born;

Yes, even he started small!

Hope this helps!

God luck,

Mitch