🥧 Pi (π)

Pi (π) is a special number: take any circle, divide the distance around it (the circumference) by the distance straight across through the middle (the diameter) — you always get the same number, no matter how big or small the circle is! That number is pi, about 3.14159…, and its digits go on forever without ever repeating.

📏 Circumference (the distance around)

C = π × d  or, since the diameter is twice the radius,  C = 2 × π × r

⭕ Area (the space inside)

A = π × r²

🎵 A Pi Rhyme

Take a circle, measure all the way round,
then divide by the distance straight through the middle you found.
That special number is pi, it goes on and on —
three point one four one five nine… and then it's not gone!

Here's a trick to remember the first few digits: count the letters in each word of
"Sky, a pond I found wonderful!"
Sky(3) a(1) pond(4) I(1) found(5) wonderful(9) → 3.14159

Want a real song? Listen to AsapSCIENCE's Pi Song on YouTube, which sets 100 digits of π to music.