Estimate Pi

Explain to students that pi is the distance around the circle that is one unit across. It's easy to estimate pi by comparing to the distance around a square or hexagon. Draw sketches such as the ones below with labels only on each diameter.

Ask students these questions and mark the lengths as students respond.

• What is the length of each side of the square? [1 unit]
• If the diameter of the circle is one unit, what is the distance around the square? [4 units]
• What is the length of each side of the hexagon? [1/2 unit]
• What is the total distance around the hexagon? [3 units]
• Is the distance around the circle closer to 3 or 4? [Closer to 3]
  

These diagrams and questions should help students remember that pi is a little greater than 3. Explain that the rounded value is 3.14 but the exact value is an irrational number. Happy Pi Day!