Did you know...that the number Pi is the ratio of a circle’s circumference to it’s diameter? That means you can find the measure around any circle and divide that number by the distance across the circle, and it will equal the special number Pi! Let’s try it by using an emoji smiley face as our measuring unit. 1. Using the template provided, move the smiley face labels around the outside of the circle. Count the total used and write this number next to “C.” 2. Using the template provided, move the smiley face labels to go across the center of the circle. Count the total used and write this number next to “D.” 3. Label the circumference and diameter using the drawing tool. 4. Using a calculator, determine Pi by dividing the circumference by the diameter. Write this number next to the equation Pi = C/d=____ 5. Is your number for Pi =3.14? If not record explaining why it is not. 6. CHALLENGE: Find a lid, measure the circumference, divide it by the diameter. Does it = 3.14?
Use the smiley faces as your unit of measure. Place around the outside of the circle. Record the total next to the circumference. Next place the smiley faces along the diameter (center) of the circle. Record the total next to the diameter. Divide the circumference by the diameter. What is your result?
The students will probably count 23 smiley faces for the circumference and 7 smiley faces for the diameter, thus giving them a circumference of 3.28 The error comes from the placement of the smiley faces. Each should barely touching one another. Are any overlapping? Is the diameter exactly 7 smiley faces or 7.5? This makes for a great discussion about precise measurement.