Posted by Angie Seltzer on 3/8/2023 to
K-5 Geometry

### Here are some fun and easy ideas for Pi Day.

- Jokes
- Contest for Memorizing Digits
- Primary Grades: Tracing Activity
- Intermediate Grades: Measuring Activity
- Middle Grades: Using Perimeter to Estimate Pi

### PRIMARY: What snake should you study on Pi Day? A pi-thon.

INTERMEDIATE: What do you get when you divide the distance around a jack-o-lantern by its diameter?Pumpkin Pi

MIDDLE GRADES: What did Pi say when someone asked it to explain Pi Day again?Sorry, I am not going to repeat myself.

PRIMARY: What snake should you study on Pi Day? A pi-thon.

INTERMEDIATE: What do you get when you divide the distance around a jack-o-lantern by its diameter?

Pumpkin Pi

MIDDLE GRADES: What did Pi say when someone asked it to explain Pi Day again?

Sorry, I am not going to repeat myself.

Contest for Memorizing Digits

Consider having a contest. (This is best for students in 4th grade or higher.) A few days before Pi Day, announce the contest for students to memorize as many digits of pi as they can. They must agree to recite (or write the digits on a board) during class. Here is list of 201 digits for reference. The winner will be the Pi Day Champion.

Contest for Memorizing Digits

Consider having a contest. (This is best for students in 4th grade or higher.) A few days before Pi Day, announce the contest for students to memorize as many digits of pi as they can. They must agree to recite (or write the digits on a board) during class. Here is list of 201 digits for reference. The winner will be the Pi Day Champion.

If you haven't announced a contest ahead of time, you could display the first 20-30 digits for a few minutes and then remove the display. Ask for one volunteer at a time to come forward and recite as many digits as they recall.

### Primary GradesHave children work alone or with a partner. Provide a round bowl, plate, or cup to each child, in various sizes, small enough to be traced on a sheet of plain white paper. Have students trace around the object to make a circle. Then have students use the ruler to draw a line across the widest part of the circle (the diameter). Next have them cut three strips of paper the same length as the diameter and tape them end-to-end.

Ask students to compare the length of the strip to the distance around the object. Is it long enough? [No matter what size objects students use, the distance around it is always a little longer than three diameters.]

Intermediate (Grades 3 to 5)Provide students with cylindrical objects such as cans or bottles. Have students make a table such as this with measurements of the diameter (distance across) and the circumference (distance around). Students should use a calculator to divide the circumference measurement by the diameter. Round to two decimal places.Ask students what they notice about the numbers in the last column. [They should be close to 3.14, an approximation for pi.]

Middle School (Grades 6 to 8)Students can use the regular polygons to approximate pi. Begin with a discussion of a regular hexagon with a diameter of 1 unit. Notice that it can be divided into six equilateral triangles. Discuss why the perimeter of the hexagon is 3. For regular polygons with more sides, students can use the sine function on a calculator to compute an approximation for pi. The sine is the ratio of the side opposite an angle to the hypotenuse. The following example shows how to find the perimeter of a 12-sided regular polygon with *d* = 1.Have students use the same method to find the perimeter of polygons with more sides. If *n* is the number of sides, they first find an angle measure *a* by dividing 360 by 2*n*. Then they will evaluate 2*n*(0.5)(sin *a*). Have students try 10, 100, 1000 sides. How many digits of pi are accurate each time?

Primary Grades

Have children work alone or with a partner. Provide a round bowl, plate, or cup to each child, in various sizes, small enough to be traced on a sheet of plain white paper.

Have students trace around the object to make a circle. Then have students use the ruler to draw a line across the widest part of the circle (the diameter). Next have them cut three strips of paper the same length as the diameter and tape them end-to-end.

Ask students to compare the length of the strip to the distance around the object. Is it long enough? [No matter what size objects students use, the distance around it is always a little longer than three diameters.]

Intermediate (Grades 3 to 5)

Provide students with cylindrical objects such as cans or bottles. Have students make a table such as this with measurements of the diameter (distance across) and the circumference (distance around). Students should use a calculator to divide the circumference measurement by the diameter. Round to two decimal places.

Ask students what they notice about the numbers in the last column. [They should be close to 3.14, an approximation for pi.]

Middle School (Grades 6 to 8)

Students can use the regular polygons to approximate pi. Begin with a discussion of a regular hexagon with a diameter of 1 unit. Notice that it can be divided into six equilateral triangles. Discuss why the perimeter of the hexagon is 3.

For regular polygons with more sides, students can use the sine function on a calculator to compute an approximation for pi. The sine is the ratio of the side opposite an angle to the hypotenuse. The following example shows how to find the perimeter of a 12-sided regular polygon with

*d*= 1.*n*is the number of sides, they first find an angle measure

*a*by dividing 360 by 2

*n*. Then they will evaluate 2

*n*(0.5)(sin

*a*). Have students try 10, 100, 1000 sides. How many digits of pi are accurate each time?

### SummaryBy doing various activities with circles, students will gain math sense about pi! Mention that ALL future work with length, area, or volume of rounded shapes involves the number pi. Have a well-rounded Pi Day!

*Angie Seltzer*

Math Curriculum WriterOwner of *K8 Math Sense*

Summary

By doing various activities with circles, students will gain math sense about pi! Mention that ALL future work with length, area, or volume of rounded shapes involves the number pi. Have a well-rounded Pi Day!

*Angie Seltzer*

Math Curriculum Writer

Owner of

*K8 Math Sense*