# Using pies to calculate pi

March 13, 2013 12:09 PM Subscribe

Ahead of Pi Day (March 14), Matt Parker tries to accurately calculate pi using pies. [SLYT] An extended version of the video will be uploaded on Pi Day, but here's your chance to go out and buy pies before that.
(Video runs 3 minutes, 14 seconds.)

Calculating (approximately) the value of pi using a string and a bicycle tire completely blew my mind as a kid. You cut the string to the size of the circumference of the tire, then fold the string across the diameter until you run out of string. Seeing that it always took three and a little bit diameters to equal the circumference, no matter what size circle you used, transformed pi from the cool looking endless number on the classroom wall into a physical reality of the universe and demonstrated to me that anybody could calculate its value, not just fancy mathematicians.

posted by zachlipton at 12:26 PM on March 13, 2013 [1 favorite]

posted by zachlipton at 12:26 PM on March 13, 2013 [1 favorite]

Ah, right... C=πD. For some reason I started out expecting him to use A=πr^2 and I was thinking, wow, that's going to be a lot of pies.

posted by Pre-Taped Call In Show at 12:39 PM on March 13, 2013

posted by Pre-Taped Call In Show at 12:39 PM on March 13, 2013

YES! Thanks in advance for a neat short video to show my fifth graders during our PI Day celebration tomorrow! (Of course, after we use yarn to measure the circumference and diameters of round objects in the classroom, a la Zachlipton).

posted by ruhroh at 12:54 PM on March 13, 2013

posted by ruhroh at 12:54 PM on March 13, 2013

Omg. I just realized that in three years' time we'll have the most accurate Pi Day in 100 years.

posted by Catchfire at 1:10 PM on March 13, 2013

posted by Catchfire at 1:10 PM on March 13, 2013

*Ahead of Pi Day (March 14),*

**Matt Parker**tries to accurately calculate pi using pies.Was Trey Stone involved in any way?

posted by The Tensor at 1:12 PM on March 13, 2013 [2 favorites]

I love this metal Golden Ratio song a lot more than I should.

posted by sparklemotion at 1:18 PM on March 13, 2013 [2 favorites]

posted by sparklemotion at 1:18 PM on March 13, 2013 [2 favorites]

I hate to be a spoil sport, but if he just made his diameter 7 pies (or some multiple of 7 pies) to start with (rather than dozens and dozens), it would have been both more accurate and faster.

posted by muddgirl at 1:50 PM on March 13, 2013

posted by muddgirl at 1:50 PM on March 13, 2013

Well, it would be faster if he used just 7 pies. That's a pretty small pie-circle.

posted by muddgirl at 1:51 PM on March 13, 2013

posted by muddgirl at 1:51 PM on March 13, 2013

Is it wrong that I kept on wondering what was in the pies and what they were going to do with a couple hundred pies after?

posted by SpaceWarp13 at 2:51 PM on March 13, 2013 [1 favorite]

posted by SpaceWarp13 at 2:51 PM on March 13, 2013 [1 favorite]

If the radius of a pizza is z, and the height is a then the volume of your pizza is pi*z*z*a.

If we're discussing pi / food things.

posted by zoo at 2:59 PM on March 13, 2013 [1 favorite]

If we're discussing pi / food things.

posted by zoo at 2:59 PM on March 13, 2013 [1 favorite]

For those of you who are teachers, there's a cool question to pose to your students about pi. Imagine the earth as a perfect sphere, with a metal band strap fitted snugly around the equator. Also, imagine a similar band strap placed around (say) an orange.

Without specifically reminding them of pi, ask them to imagine cutting the band strap on the orange, and inserting (say) around an inch or so into it. Visualize in your mind how 'high' off the surface the strap will now be.

Once everybody has that image in mind, now do the same thing with the band strap around the earth - ask them to insert the same inch, and then visualize how 'high' the strap will be.

It will be a very rare student who will get the correct answer ...

posted by woodblock100 at 3:26 PM on March 13, 2013

Without specifically reminding them of pi, ask them to imagine cutting the band strap on the orange, and inserting (say) around an inch or so into it. Visualize in your mind how 'high' off the surface the strap will now be.

Once everybody has that image in mind, now do the same thing with the band strap around the earth - ask them to insert the same inch, and then visualize how 'high' the strap will be.

It will be a very rare student who will get the correct answer ...

posted by woodblock100 at 3:26 PM on March 13, 2013

*Ahead of Pi Day (March 14), Matt Parker tries to accurately calculate pi using pies.*

Was Trey Stone involved in any way?

Was Trey Stone involved in any way?

Trey stone is bit over 6 pi kg.

posted by novalis_dt at 3:38 PM on March 13, 2013 [3 favorites]

« Older 99 Problems But 16-bit Ain't One | Turnament! Newer »

This thread has been archived and is closed to new comments

Using pies to calculate piMarch 13, 2013 3:09 PM Subscribe

You couldn't have waited five more minutes?

posted by ricochet biscuit at 12:17 PM on March 13, 2013 [12 favorites]