Dodecahedron Day

Dodecahedron Day was founded in 2004 by Dr. Vince Matsko and Todd Klauser in Quincy, Ill. The intent was to have older students go into the classrooms of younger students and teach them about dodecahedra and how to build them. They took students from the high school to fifth- and sixth-grade classrooms and exposed them to the world of three-dimensional geometry.

Dodecahedron Day is celebrated on December 5 because there are 12 5-sided polygons (pentagons) on a regular dodecahedron.

On Dec. 5, the Princeton Library will celebrate Dodecahedron Day for the first time, offering students the chance to explore three-dimensional geometry, learn about Euler’s formula, and construct a dodecahedron out of paper.

"Dodecahedron Day is an opportunity for students to experience the wonder of building their own geometric models," says Hanna Lee, director of youth services at the Princeton Public Library. "Students engage in mathematical discovery and gain a more positive attitude toward mathematics."

Dr. Matsko is currently a math teacher at the Princeton International School of Mathematics and Science. He says it is really important to get students excited about mathematics at an early age, and participating in Dodecahedron Day is a great way to do so.

"We’re celebrating Dodecahedron Day both in local area schools and the Princeton Public Library," he says. "I am involved with the Mercer County Math Circle, and I see how many students can be reached at a location like PPL. This seemed a natural choice for one of our venues for the day."

Aside from going to local schools, Dr. Matsko will be conducting activities at the library, which include: a) puzzles with pentominoes (there are also 12 pentominoes, each made with five squares); b) constructing paper models of dodecahedra; and c) constructing polyhedra with plastic snap-together polygons.

"These activities expose students to the joys of hands-on mathematics. They get to see that mathematics is not simply a set of textbook problems to solve, but a real, live endeavor," he says. "And students will be able to take their dodecahedra home with them."

Dr. Matsko moved to the area this year, so this will be the first time that Dodecahedron Day will be celebrated in Princeton, although he has run similar activities elsewhere since 2004.

"Vince Matsko approached us with his idea, and since the Princeton Public Library is always looking to support engaging enrichment programs for children and youth, we jumped at the opportunity," Ms. Lee says. "This fall, we have partnered with the Princeton University Math Club and community member/educator Harini Subrahmanyam Fredrickson to offer Mercer County Math Circle (MC)2, a mathematic exploration series for middle and high school students. Dodecahedron Day allows the library to offer fun, innovative, math-based activities to younger students as well, while strengthening our community partnerships."

Dodecahedron Day, which runs from 3 to 5:30 p.m., is open to students of all ages, but it is probably best-suited for students in grades 3-6. Those interested in participating are encouraged to register online at

"We often hear about STEM (Science, Technology, Engineering and Math) initiatives occurring in classrooms or in schools. I think it’s great that this push is happening at school, but it’s also essential that children have fun and unexpected encounters with learning outside of the classroom," Ms. Lee says. "Dodecahedron Day allows children to grapple with some complex math concepts in a dynamic, hands-on way, which gives depth and richness to their regular learning."

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