Pi(e) Day!

Simply Homeschool / 9 March 2023


Did Someone Say Pie?!?  

March 14th is Pi Day. It’s the perfect opportunity to spend some time together baking a delicious treat and playing with maths. 

Maths is a common source of anxiety for many learners - and for many adults too! We can reduce our anxiety by having fun with maths; approaching numbers playfully with concrete materials that learners can move around, touch and see. And what’s more fun than getting to eat pie at the end?! 

So, what is Pi anyway? And why March 14? 

Mathematician William Jones created the term Pi and first used the symbol π. Pi is the first letter of the Greek word for perimeter (perimitros). That’s one thing Pi can help us find out - the perimeter (measurement around the outside) of a circle, or the circumference. Tasty and helpful! 

Although Jones named Pi, he certainly didn’t invent it! The concept of Pi has been used to calculate the circumference of a circle in many different ancient cultures - as far back as the Ancient Babylonians over 4000 years ago!  

Most people know the first three digits of Pi, 3.14. Which is why March 14th, (3/14), is Pi Day! 


Bake a Very Tasty Pi(e) 

Cooking incorporates so many practical math skills and is a delicious way to make Pi Day fun! We’ve even included some fun maths activities to do with your pie (if you can resist not eating it straight away, that is!) 





  • 1.5kg apples – Granny Smith work best 

  • 100g brown sugar 

  • 1 teaspoon cinnamon 

  • 3 tablespoons butter 

  • 4 tablespoons of all-purpose (plain) flour 


  • 400g all-purpose (plain) flour 

  • 250g very cold butter, cut into cubes 

  • 50g caster sugar 

  • 3 tablespoons iced water 




  1. Peel, core and slice the apples, about half a centimeter thick. 

  1. Combine the prepared apples with the brown sugar, cinnamon and butter in a large saucepan. 

  1. Cook over medium-high heat, stirring often, until apples are softened but still holding their shape - about 15 minutes. 

  1. Add the flour and stir to combine. Remove pan from the heat and set aside to cool. 

Crust and Assembly: 

  1. Add the flour, sugar and cubed butter to a food processor*. Process until combined and resembles large crumbs. 

  2. With the motor running, add the iced water a tablespoon at a time (you may not need it all) and process until the dough forms a ball. 

  3. Turn the dough out onto a lightly floured surface and use your hands to form it into a smooth lump. Cut off one third. Push the two dough pieces into flat discs. Wrap in plastic wrap and refrigerate for 30-60 minutes. 

  4. Print and cut out the Pi symbol template**. 

  5. Remove the plastic wrap from the larger disc and use a rolling pin to roll it into a circle that is approximately 4mm thick. This will be the base of your pie. 

  6. Gently lay the pastry into a 23cm pie tin and push into the corners. Either fold the excess dough to form a rough crust or trim the excess and reroll. Cut and braid for a braided crust. Place the prepared pie case in the freezer for half an hour. 

  7. Roll out the smaller disc to approximately half a centimeter thick. Lay the Pi symbol template over the pastry and use a knife to cut around it. 

  8. Carefully transfer the pastry Pi symbol onto some baking paper and freeze for half an hour. 

  9. Preheat oven to 180 ̊C.  

  10. Remove prepared pie case and place baking paper on top of the dough. Fill with baking weights, dry beans, or uncooked rice. Bake for 15 minutes. This is called blind baking and will ensure your pie crust doesn’t get soggy when you add your apples. 

  11. Remove the baking paper and weights and prick the base with a fork a few times. Return to the oven for a further 5 minutes. 

  12. Remove the base from the oven and fill with the prepared apple filling. Be sure to push the filling into all the corners. Cover well with foil and return to the oven for 45 minutes. 

  13. Remove the foil and bake for a further 15 minutes.  

  14. Cook the Pi symbol on a separate tray for 15-20 minutes or until golden. 

  15. Allow the Pi symbol to cool for 10 minutes and then carefully transfer to the top of your Pi(e). 


Recipe Notes

* If you don’t have a food processor, simply mix the flour and sugar together and then rub the butter through with your fingertips until it resembles large crumbs. Add the water and then mix with a spoon, swapping back to hands once the liquid is mostly absorbed. Mix until the dough is a smooth ball. Refrigerate for the full hour as the extra time mixing will have warmed the butter. 

** See attached template. 

Download Pi Template Here

Now for the Maths! (Remember, there’s pie at the end!) 


How do you use Pi to calculate the circumference of a circle? 

You can calculate the circumference of a circle by multiplying Pi by the diameter of a circle (the measurement straight across a circle passing through the centrepoint).  

Or you can multiply Pi by two and use the radius (the measurement from the centrepoint of a circle to any edge). 

  • The equation looks like this: π×d = circumference 

  • The equation looks like this: 2π×r = circumference 


You can use Pi to calculate the area of a circle too! 

To calculate area, you need to square the radius and multiply by Pi. 

  • The equation looks like this: π×r 2 = area 


Maths Activities: Apply Pi to your Pi(e)! 

If you don’t have time to cook a pie from scratch, you can use a pre-made base and canned filling, a bought pie, cake, pizza, or any other round food! It’s all deliciously educational. 


Calculate Circumference 

  1. Use a tape measure or ruler to find the diameter of your Pi(e). 



  1. Cut three pieces of wool the length of the diameter.



  1. Carefully tape the wool pieces together to form a circle. Try not to overlap them.



  1. Lay your circle over top of your Pi(e). It will nearly be equal to the circumference. Why is this circle a little smaller? It's the missing digits after the decimal point!



  1. Calculate the circumference using Pi.  
    π×d = circumference 

  2. Divide your circumference by 3. How much longer than the diameter was it? Find the difference 
    (circumference ÷ 3) - diameter = difference 

  3. Multiply the difference by 3 and cut a string that length. 

  4. Carefully open your existing circle and tape in the extra piece. It should now fit the circumference of your Pi(e) perfectly! 


Calculate Area and Fractions 

  1. Calculate the area of your Pi(e)  
    π×r 2 (Remember r stands for radius, which is half of the diameter) 

  2. How many slices will you cut your pie into? What will be the area of each slice? How would you work that out? If you cut it into sixths, is one slice more or less than two eighths? How would you work that out? 


Here’s a challenge for you...  

Imagine you arrive at the pie shop looking to buy a yummy dessert. When you arrive, you find they have a special running. You can buy one 23cm diameter apple pie for $20 or you can buy two 16cm diameter pies for the same price. Which offers better value for money? The single apple pie or the pair? 


Why calculate the circumference of a circle? 

Why were ancient mathematicians concerned with calculating the circumference of a circle anyway? It wasn’t just for fun, or to provide some challenging problems for ancient learners. Pi is vital in building projects - pillars, arches, bridges, pipes and more!  

Pi was even used to plan the building of the Great Pyramid of Giza! Today Pi is used in biology, physics, chemistry, astrophysics, astronomy, probability, and so much more. 

Pi is what mathematicians call an irrational number. That means that the numerals following the decimal point are never ending; there are an infinite number of numerals in Pi! If you wrote a digit of Pi every second for your entire life you could never reach the end of Pi.  

NASA only uses the first 15 digits in its calculations though. So, we don’t need more than that for quite accurate calculations! And if you want to memorise the first 15 digits, here they are: 

π =3.14159265358979 


Other ways to celebrate Pi Day: 

  • Hold a family challenge to see who can memorise the most numbers of Pi. Or work together to memorise the first 15 digits.  

  • Create some colourful paper bunting displaying the first 15 digits of Pi to hang up in the house. 

  • Collect as many round objects around the house as you can. Measure the circumference using a string, then divide the circumference by the diameter. Watch as Pi appears again and again! The more accurate your measurements, the closer you’ll get to Pi. 

  • Calculate the circumference and area of each round Australian coin. 

  • Learn how to apply Pi to finding the volume of a cylinder. Compare the volume of various mugs to discover which will hold the most hot chocolate.  

  • Hold a Pi Tea! Enjoy your pie (or other round treat), and hot drinks, in mugs you’ve found the volume of! While you eat and drink, play a math board game, challenge one another with math riddles, share Pi jokes, or work on some sudoku together.  

  • Read ‘Sir Cumference and the Dragon of Pi’ by Cindy Neuschwander 

  • Make colourful paper pies using construction paper and create a play Pi(e) shop. 

  • Highschool level learners can try some of NASA’s Pi-themed tasks. 

  • Use Pi to inspire some writing - write in Pilish; the number of letters in each successive word must be equal to the next number in Pi. For example: 
    Can I love a maths challenge? 
    (Can has 3 letters, I has 1, love has 4, a has one, maths has 5, challenge has 9.)
    You could write a poem, a story, instructions, anything! 


Happy Pi Day!! 


< Back