When is a letter actually a number? In this BrainPOP movie, Tim and Moby introduce you to the magical little number called pi! Discover where the concept of pi comes from, what ratio it represents, and why all circles have it in common. You’ll also find out why we use a Greek letter to represent the number, what an irrational number is, and why irrational numbers can’t be written as fractions. Best of all, you’ll figure out how to use pi to find the circumference and the area of a circle. Those ancient Greeks sure were smart!