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###### Inside:  What is the meaning of Pi? Anywhere you see circles, the constant Pi comes into play. Sound waves, river bends, and pie plates are impacted by the constant 3.14……Read more about this irrational number and learn how to prove Pi is real.

What is the meaning of Pi?  You would be tempted to think of warm crusty pie with a generous dollop of ice cream.  That’s what my first thought would be.  There is a pi day.  I think there is even a pie day for those foodies out there.  But the Pi Day we’re talking about here is not for eating Pi, although you could make pie baking a part of the festivities.

March 14, or 3/14 is the day to celebrate everything Pi.  But what in the heck is Pi if it’s not pie?  For those of you not in the know, Pi is a number related to circles.

When you make a habit of measuring circular objects, you find that a circle is about 3 times its width.  The Old Testament in 1 Kings 7:23 refers to a circular pool being 30 cubits around and 10 cubits across.  Even the ancient scholars had a solid idea about Pi.

## Meaning of Pi

Pi is a constant.  It is found by looking at the ratio of a circle’s circumference to its diameter.  In honor of Pi Day which happens each 3/14, we’ll round this constant to 3.14.  However, Pi is an irrational number, meaning it is a real number with an infinite number of decimal places that don’t repeat in any particular pattern.  The symbol used to represent Pi, π, is the 16th letter of the Greek alphabet.

But again, what is the meaning of Pi?  It is a constant but how is it calculated?  Pi refers to the ratio of the distance around a circle – its circumference – to its diameter.  In other words,

where C = circumference of circle and d = diameter of circle.

## Applications of Pi

Pi is used in a number of practical applications.  In nature, it is used when measuring anything with curves like:

• ocean waves
• light waves
• sound waves
• river bends
• radioactive particle distribution

In science, Pi is applied in:

• fractals
• thermodynamics
• cosmology
• electromagnetism

## Prove the Pi Constant with Pie!

Do you want to celebrate Pi day in your classroom or home school in a meaningful way?  Then make it fun and bake a pie.  But have the students do the measurements to prove the pi constant before you eat.  Also, have the students figure out the volume of their pie using one of the formulas below.  After all, a pie plate is just a cylinder in disguise! After the kids have successfully done their calculations using pi, celebrate with a pie party.

Try this idea.  Have the students gather circular objects from around the classroom.  Pie plates, sauce pans, frying pans, drinking glasses or mugs, buckets, circular sand toys are ones that come to mind.  With a chart on the board, have the kids do the measurements to calculate pi and record them.  How close to 3.14 are their calculations?  Does the average of all calculations come closer to 3.14?

## Other Calculations Using Pi

For older students, download the worksheet provided in this post.

The above activity is included with a chart to use.  As well, some word problems using pi are included.  Pi is a super important constant in math and science.  It is used in calculating:

• the surface area of a cylinder:  2πrh + 2πr²
• volume of a cylinder: πr²h
• circumference of a circle can also be calculated: 2πr
• area of a circle: πr²
• volume of a sphere: 4/3πr³
• surface area of a sphere: 4πr²

You should have a better grasp of the meaning of pi after reading this post.  Now get out there and apply this constant to practical areas of your life.  How big is that pie you feel like consuming in one sitting?  How much paint will you need to cover a cylindrical craft project?  Better yet, how much frosting will you need to perfectly frost that celebration cake?  If you need a great worksheet for your science class or home school download my worksheet here.

Let me know in the comments how you’ve used your new knowledge of Pi!