Pondering and Playing with Pi

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You remember Pi with its familiar symbol π, don’t you? Geometry class, right?

We sheepishly admit that we needed a bit of a refresher to recall what pi is and how it is used. Pi equals the circumference of a circle divided by its diameter. It is a constant, but with an infinite number of digits. For basic calculations, most people shorten pi to 3.14. You can use pi to calculate the circumference of a circle: just multiply pi by the diameter (or by 2 times the radius). And the formula for the area of anything circular is pi times the radius squared. Pi and these calculations were formulated thousands of years ago, and unlike some modern technology, they still work. Pretty cool!

Pi Day is celebrated every year on March 14th or 3/14 because the date matches the first 3 digits of pi. OK, but what’s all the extra fuss about Pi Day this year? Well, this year for the entire day, the first 5 digits of pi are represented (3.1415 or 3/14/15) AND at 9:26:53am and 9:26:53pm the date and time will represent the first 10 digits of pi! 3.141592653.

This phenomenon happens only once per century. Now that’s why math nerds will be screaming from the tree tops on Saturday (you’ll hear them if you listen closely).

Now let’s experiment by calculating the volume of an orange (pretending it’s perfectly spherical) using pi.

Orange Pi

The formula is:


Since we couldn’t easily measure the radius of the orange without cutting into it, we measured the circumference of the orange. We took some red waxed string that we use to tie our dried fruit boxes and wrapped it around the outside of the orange. It measured 9.5 inches. Then we applied the formula Circumference = 2πr, and solved for r (radius).

9.5 = 2 (3.14) r

9.5 = 6.28 r

9.5 = r


Radius = 1.51

Now we can plug the radius number into the formula for volume.

V = 4/3 (3.14) (1.51)3

V = 4/3 (3.14) (3.44)


V = 4/3 (10.80)

V = 4 (10.80)


V = 14.41 cubic inches


We’re reminded just how much fun geometry can be!


One final thought about pi: why does it seem to be enveloped in such mystique? Is it that it is a number that never ends making us contemplate the concept of infinity? (Pi’s digits have been generated by super-computer to trillions of digits beyond the decimal point with no end in sight.) Or is it that pi makes us reflect on what our world would look like without pi – no wheel, tunnels, suspension bridges, etc. And while pi appears to be a collection of random numbers, this has never been proven. So some scientists wonder, “Are some patterns hidden in the number sequence, waiting to be discovered, that can help us better understand biological paradigms?” Food for thought …


And don’t forget that 3/14 is also Albert Einstein’s birthday!! Go wild!




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  1. Dear Two

    Your reflections on pi inspired me to arrange to stand at the dead center of Columbus Circle, at the appropriate moment on 3/14, in the hope of discovering a new dimension. The depressing realization that Columbus would refuse to move over forced me to a changed ambition: find a new pie.

    Hope the Golds continue to gleam.


  2. Wonderful to read this — not that I understood every word or numeral. Rob and I celebrated True Pi Day in Big Sky, Montana, with our daughter — who was getting married to her math major fiancé! He gave a toast at 9:26 and there was much merriment and dancing, cake and pi(e).

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