# What is Pi Day?

Every year on March 14 math lovers all over the world celebrate Pi Day! Many celebrate this special mathematical day with Pie, but today we are focusing on Pi. They may sound the same but you can’t eat this Pi! Let’s explore the world of Pi and Math with a lesson and some easy, no prep, Pi Activities.

## Celebrate Math and Pi on March 14

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## What is Pi?

Pi is a Mathematical Constant – This means that no matter what measurements you’re comparing the answer will always be the same.

Pi is the ratio of a circle’s circumference to the diameter of a circle. When solved as an equation the solution is always the same no matter what size the circle is, big or small, the answer will always be the same.

#### The digits of pi are: 3.141592653589793238462643…

The number goes on and on FOREVER without any repeating pattern to the numbers. It has a never-ending number of decimal places. Hard to imagine, right?

You might think – well that’s not rational – and you’re right – that’s why Pi is an irrational number! As an irrational and transcendental number, it will continue infinitely without repetition or pattern.

To keep things simple, for most calculations we use 3.14 for Pi which is represented by the Greek letter π.

Look closely at that explanation you might see why we celebrate this amazing number on March 14th – 3.14! Pi Day!

## What is Pi Day?

Where did the concept of Pi day originate? Physicist Larry Shaw, organized the very first Pi Day celebration way back in 1988 at the San Francisco Exploratorium, a science and technology museum. Fast forward to 2009 and in the USA, the U.S. House of Representatives created a new national holiday as they proclaimed March 14 National Pi Day.

Why March 14? Because March is the 3rd month, so the date written numerically is 3-14. Pi Day gained a huge amount of popularity in 2015 when the date was 3-14-15 and has maintained that popularity in classrooms and homes since then.

March 14 also happens to be Albert Einstein‘s Birthday!

Pi Day is a fun way to encourage an interest and excitement for mathematics. With mathematicians, teachers, librarians, scientists, families and even bakeries all joining in on the Pi fun!

## A quick classroom vocabulary check on Pi

• Pi: The ratio of the circumference of a circle to the diameter of a circle.
• Circumference: The distance around something.
• Diameter: The distance through something.
• Ratio: A comparison of two quantities of the same units.
• Fraction: A part or piece of something.
• Rational Number: A rational number can be written as a ratio (4:1). A ratio can be written as a fraction where the numerator or top number and the denominator or bottom number are both whole numbers but neither number is zero.
• Irrational Number: An irrational number is a number that can not be expressed as a ratio or fraction. It is a decimal that goes on infinitely with no repeating pattern.

## Pi Day Printable

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Pi can be a confusing concept for anyone – so how can you engage kids and get them excited about finding Pi for themselves and interested in cool math concepts in general? Tell the students that you’re going to investigate a mathematical phenomenon!! Then go on an adventure.

Pair off your students and arm each group with a measuring tape, a long piece of string and a recording sheet and pencil. Now walk all over the school trying to spot circles. Each time a group finds a circle, measure the circumference and diameter of the circles and record them on your sheet. Try to have the different groups find different circles so when you compare the answers you have a lot to compare.

When you return to the classroom have the students figure out Pi: for each circle – Pi=Circumference divided by diameter. As each equation is solved they should start to notice the pattern – every time they solve the answer will be exactly the same for every circle you found! AMAZING!

## Simple Units of Measure Pi Activity

If an adventure is too much – or your kids aren’t great with rulers or measuring tapes yet – find another unit of measure – skittles, M&Ms, beads and pom poms all work – something that is uniform in size and that you can line up around circles and count.

Have the students trace circles onto a piece of paper and then draw a line right across the center. For little kids it is helpful to draw a dot on one side of the circle so they know where to stop and start. You could even do a dot or the same color measuring device on each side of the diameter line.

Here you can see we lined the circle with small pom poms. Pom poms are perfect because they are easy to handle, don’t roll away on their own, and aren’t accidentally snacked on when you’re not looking! Once you figure out how many items you need on the outside and then across, line them up next to each other so you can easily see that you need 3x plus a little bit of the across to equal the around!

## Demonstrating Pi with Paper

Another super easy way to show this is to wrap a strip of paper around (circumference) your item and cut it so the ends meet then lay another strip across the center of the item and cut it to the diameter. Then cut yourself two more strips to match the size of the diameter piece. This way you can easily lay out the pieces so that the kiddos can see that it takes 3 and a little extra to equal the longer strip!

Another fun activity is to make a classroom paper chain. Use different colors to represent different digits 0-9 then see how long you can make the paper chain – you could make it a class level or whole school activity passed from class to class- because just like Pi a paper chain could potentially go on forever!

Nothing says party like food – so why not make it a real party by including circle snacks like cookies (oreos are a perfect circle!) pizza pie, apple pie or other fruit pies! You could even throw a bake sale for the math club with all different kinds of pie! The possibilities are endless!

## Pi Craft Idea

Grab some beads with numbers on them, and create a bracelet or necklace with the numbers of Pi. Then show off your mathematical jewelry!