It’s winter and even in sunny Queensland where I live it’s getting chilly at night and sometimes even during the day. One of my favourite winter desserts is warm apple pie with custard. Sorry, I can’t send you an apple pie through your computer screen, but I can tell you what it has to do with maths!
Most pies are circles and the number pi has a LOT to do with circles. But before we can go further, you’ll need to know some circle anatomy: anatomy is just a fancy word meaning the “names of the parts.”
We’re going to see exactly how the number pi is related to circles (and edible pies!) in a bit, but first, I want you to have a go at this experiment. Find something that’s round but also has a flat top and bottom(a plastic lid from a peanut butter jar is ideal) and a piece of string that is long enough to wrap around the object you chose at least once.
Now, wrap your string around the object exactly once and mark where the end of the string meets the rest of the string. It will probably be easiest if you use a marker to do this. Mark BOTH the end of the string and the place where it meets the rest of the string. You have just measured the circumference of your circle!
Now, we want to measure how many diameters of the circle long the circumference of the circle is. To do this you will take your marked piece of string. Start with the marked end and line it up with the edge of the top of your circle object and then lay the rest of the string along the top of the object so that is passes through the centre of the circle and then let the overhang just sit on the table. You don’t have to be super exact but try get as close as you can. Plastic lids often have a bit of a ‘dimple’ or ‘bump’ in the centre so this can help!
Now, pinch the string at the start of the overhang, That is, at the edge of the lid that is opposite to the marked end of the string. Drag the string across the lid until your pinched finger is above the side of the lid where the end of the string was. Hold the pinched spot on that edge of the lid while you use your other hand to make sure that the string is lying flat across the lid again.
Keep doing this until you get to the second mark on your string. How many times could you move the string? You should find that the circumference of your circle is “three and a bit” times as long as the diameter of the circle.
Now, I’ve got a secret for you. You’ve just discovered the magic of pi (π)!
Pi is a special number in maths (and science) that belongs to a group of numbers called physical constants. Pi is the ratio of the circumference of a circle to its diameter. If you don’t know what a ratio is, don’t worry. All you need to understand right now is that if you do the above experiment again on ANY circle object, you’ll get exactly the same result every time!
And what about that yummy name? Why does it sound like a pie that you eat? Well, for some reason scientists and mathematicians really like the Greek alphabet and pi is just the name of a Greek letter which looks like this: π. Does that look familiar? Hint: look at the Milestone Maths logo!
For parents
For more engaging lessons like this one, checkout our products page for the full Milestone Maths curriculum. Milestone Maths is the first print based maths curriculum designed for Australian home schoolers by an Australian home schooler. We focus on building confidence, understanding and mastery through discovery and hands-on learning.
Leave a Reply
You must be logged in to post a comment.