What is pi?Explained for kids

The short answer

Imagine cutting a string that reaches straight across the middle of a circle. It would fit around the edge a little more than three times. That number, about 3.14, is called pi.

Try these at dinner

If you cut a string the width of your plate, how many times would it fit around the edge?
Do the digits of pi ever end?

What Nana says

Mmm. Oh, how I love pie!
But did you know there's another pi? It's not a pie. It's a number.
And it's magical: it's hiding in every circle in the world. Want to find it?
If I walk all the way around my plate... that's the way around. Grown-ups call it the circumference.
And if I cross to the other side, right through the middle... that's the way across. The diameter.
So how many acrosses fit in one around? One... two... three... and a tiny bit more!
About three!
And you want to know the magical part?
A hoop? Three and a bit. A coin? Three and a bit. A ball? Three and a bit. The sun? Three... and a tiny bit more!
Every time!
That "three and a tiny bit more" is called pi. Three point one four... And the numbers after it never end. They just keep going... and going... and going!
Let's see who was listening!
Hey, Opa. How many acrosses fit in one around?
What do you think?
About three! Opa knew it.
And do the numbers in pi ever end?
Never! They go on forever.
Try it yourself! Grab a plate and a string, wrap it around, lay it out, and count. Then tell your class you found pi. The number.
...And the pie.
Time for a little nibble!
"Look around. There's magic hiding in your day. Can you find it?"