# Science with Shields: Episode #69 – Celebrating Pi

ALTOONA, Pa. (WTAJ) — In this episode of Science with Shields, Christy Shields celebrates Pi Day!

What you need:

1. Household items in the shape of a circle
2. Measuring tape
3. Calculator
4. Compass

Instructions:

Pi Day happens on March 14th (3.14) each year to celebrate the mathematical irrational number π!

π = 3.1415…

For this experiment, find a few household items that are in the shape of a circle. We will be calculating pi which is the circumference (C) of a circle divided by its diameter (D).

The equation looks like this:

C ÷ D = π

I used a pizza pie for an example. Measure the circumference of the circle with your measuring tape (around the whole circle) and write that number down. For example, I got 129 cm. Next, measure the diameter of your circle (straight down the middle) and write that number down. I approximately got 40.5 cm. Now, divide your circumference by the diameter and see what you get. In this example, 129 cm ÷ 40.5 cm = 3.18 cm. This is around the number π which equals 3.14! Due to our measurements not being precise, we will get an approximation.

You can even try this backwards, or manipulate the equation.

The equation will look like this:

D × π = C

Take your next object and measure the diameter. For my drawn circle with a compass, the diameter was 15.5 cm. We know that π = 3.14, so if you take your diameter of 15.5 cm × π, it will equal around your circumference! So, 15.5 cm × π = 48.67 cm. Check your work by measuring the circumference. When the circumference is measured, I roughly got 50 cm which is close to the 48.67 cm! Again, our measurements are not perfect, so we will get around pi, but it will not be perfect.

Science

Pi (π) is an irrational number useful in math. It is the ratio of a circle’s circumference to its diameter. Pi goes on for infinite!

π = 3.141592653589793238462643383279502884197169399375105820974944592……

It dates back to Egypt in 1650 BC, but the symbol π was created by Leonard Euler in 1737.

Pi is so important for math equations. In weather, we use it a lot! For example, the Earth is a sphere (3D circle), so pi is used in the computer models we use to forecast the weather.

Happy Pi Day and make sure to share with us how you celebrate on March 14th!