Updated March 2017 (Originally published: Oct 3, 2014)
This morning, on the train journey back home, and inspired by Holly Smale‘s reading from her series of books at the Hertford Children’s Book Festival, I started to wonder if I could use rhyme effectively, to teach children something useful. What about PI? Well …
UPDATE: The wonderful DeafBoyOne has turned the rhyme (further below) into this song:
This is my first stab at doing just that – it’s taken me a few hours to write on my phone …. I’m still on the train, posting from my phone, so please excuse any typos and I’m not even going to attempt formatting(!!!), but let me know if you like it by leaving a comment, and please remember this is just a first draft – I imagine it as being an illustrated rhyme at some point.
Mmmm PI – by Eric James
In Maths there’s a number. This number’s called PI. But why name a number? I’ll demonstrate why! And when I have finished you may be astounded, your maths skills will be just that little more … ’rounded’ (*ahem*) Find any old circle: a pan or a pot, a frisbee, a saucer, whatever you’ve got. Get one ball of string, grab some scissors and glue. You’ll need them for what we are going to do.
We’re going to measure a distance with string, in order to witness a curious thing – no matter the size of the circle selected, there’s something about every one that’s connected.
First measure the length of your circle’s inside. You’ll start at one edge and you’ll go side-to-side. (Go straight through the part where the circle’s most wide, and try to be accurate. Measure with pride!)
Then snip at the string with your scissors SNIP SNIP! And look at the string that you have in your grip, admiring its length as you hold it out straight. That’s called the DIAMETER. Isn’t it great!!!
“But what use is that?” I hear some of you squeal. “A length of old string. Tell me, what’s the big deal?” (Well, that’s just the thing that I plan to reveal!)
We’ve one bit of string, but we need to have four. So, please make 3 more, just the same as before. And when you have finished, you’ll want to ensure all lengths are the same. Yes I know – what a bore!
Now this is the fun part, so here’s what you do: you cover the edge of your circle with glue, and stick on the string (pieces one, two & three). You’ll end up with one tiny gap, just like me!
That forth bit of string is too large is it not? Chop off what you need – just the tiniest dot. Then fill up that gap so the gap is no more. You used 3 whole pieces … and 0.14 <—- [nought point one four]
Now pick a new circle. You know what to do … you measure the string and you slap on the glue. You stick on that string and then just like before, you find you need 3 and a bit out of 4!
But if you are shouting “That’s NOT my result!” your circle is wonky or *you* are at fault! I know this for certain. Of that I am sure. You see, I know PI, which is 3.14!
This value is constant. It always applies. Each circle obeys it, no matter the size. And rather than always say “three point one four”, we just call it PI, as it’s less of a chore.
To find the circumference (around the outside), we measure our circle (to find out how wide), and multiply that by our figure called PI. I hope that explains it. I’m off now. Bye bye.