Celebrating math with festivals
Math is irresistible and fascinating, and it turns out, there’s a bigger community for it, too. We host a LoveMath! festival for girls in the fall and a spring festival for all. If you’re less familiar with the recreational math world, you’re in for a treat! We solve logic puzzles and brain teasers (think magic squares and tangrams), work together in escape rooms, and make mathy art. The festivals take place at Proof. More info on the way!
LoveMath! Festival for Girls
Saturday, November 7, 2026
Spring math festival
Saturday, April 10, 2027
The Pickleball Problem
One day, Hedgie Wedgie went to the Proof Open, a pickleball contest held over 48 consecutive days. He liked watching the match so much that he invited his twin, Wedgie Hedgie, to join him the next day. They had such a good time that they each invited one more hedgehog to watch with them the following day. Each successive day, the number of hedgehogs continued to double—this was the hottest invite in town!
On the 16th day, Hedgie noticed that their numbers were starting to fill a small but not insignificant corner of the arena. Being the curious and clever hedgehog he is, he wondered how long it would take for hedgehogs to completely fill the arena. After doing a lot of thinking, he accurately calculated it would take exactly the number of days the contest was going to last. (What a coincidence!)
On which day was the arena half full of hedgehogs?
Think about the problem backwards from day 48.
Bjorn Impersonates a Hedgehog
Bjorn is a lovable shark who really wants to be a hedgehog, so he puts on a pretty convincing costume, and attends a small summit of hedgehogs at an otherwise undisclosed location. Once everyone arrives, they look at each other with suspicion: Only 26 hedgehogs were invited, and 27 were in attendance. Clearly, there was an imposter!
After some murmur and argument, Hedgie Wedgie declares he has a way to find the imposter: As everyone knows, all hedgehogs weigh exactly the same, and Bjorn, after making sure he weighed that precise figure, had forgotten that the costume added weight. Hedgie pulls out a simple balance scale and figures he'll catch the imposter. But there is a note on the scale: It is only accurate for the first three weighings, due to a strange quirk in gravity at their secret location. After that, it's a bust.
How does Hedgie Wedgie find the imposter?
What if there were only three hedgehogs and one weighing?
Hedgie Wedgie “Nose” the Answer. Do you?
Last week, at the Comprehensive Convention of Clever Creatures, exactly 20 hedgehogs attended (including myself). Each hedgehog brought a porcupine friend (I brought my best friend Porcia Porcupine, of course!). In the first few minutes, the creatures milled about and rubbed noses in greeting with one another, but no one rubbed noses with the friend they had arrived with (they already knew each other!).
When everyone had settled down and was ready to get started, I asked each of the other 39 attendees (including my friend Porcia) how many creatures they had rubbed noses with. Strangely enough, no two creatures gave me the same answer!
How many creatures did Porcia rub noses with?
For this one, you’ll need to “struggle with it”!
Camping out with math
Camp Lemma is our one-week summer day program for rising 4th-9th graders who love math. Our campers learn, create, and play in a mathematically-rich environment, surrounded by like-minded peers and guided by a fairly friendly staff of teachers and camp counselors (who are themselves Proofniks).
Activities allow students to explore a variety of mathematical topics outside the standard middle school and high school curriculum. From polytopes and secret codes to probability paradoxes, we give students a sense of just how varied and fun math can be.
More info for Summer 2027 coming soon!
Developing math teachers
We host the San Francisco Math Teachers’ Circle throughout the academic year. Think of it as professional development + a mini math festival all rolled into one. Meetings are held monthly on Saturday mornings (typically 10:30am–1pm) for anyone interested in exploring accessible, exciting topics in mathematics.
For more information, visit the SFMTC’s website here.
In math we trust
The math world is pretty connected, and we like providing a space where it can happen — and going outside our campus to engage the larger world of math. Our school, board, teachers, and students have all collaborated with like-minded organizations like OMEGA; recreational math festivals like the Julia Robinson Math Festival and Gathering 4 Gardner; summer camps like MathPath,Mathcamp, and Math in the Mountains; and contests both national and local, such as the American Masters of Mathematics and the Bay Area Math Olympiad.
Most recently, we hosted the Bay Area Math Out Loud Olympiad, or BAMOLO, a competition modeled on the UW Math Olympiadwhere participants walk judges through how they solved problems. This special olympiad started nearly 20 years ago in Seattle, and 2026 was the first year it took place outside of Washington.
“Volunteering at math festivals has always been really special for me, because my first experience with Proof was at a math festival.”
“I thought it was cool to meet new people at a festival with similar interests to me.”
“Helping others grow is really great”
“Watching kids thrive, make friends, and develop their interest in math at Camp Lemma is especially rewarding”
“I enjoyed getting to meet younger kids who loved math and enjoyed being able to talk to them over a game of chess.”
“Seeing the moment when something suddenly makes sense is always so special.”
Mailing out math and more
Proofniks like to jump into the mix and pursue their own outreach. They’ve staffed tables at Gathering 4 Gardner, attended plenty of Maker Faires, and have served as residential counselors at summer math programs. Last year, two seniors won a grant to put together a curiosity box of fun math problems to mail out. It was a huge undertaking, and a group of returning Proofniks are going to carry that project forward.
Catalina, 11th grade
Outside of the regular school year…
I’ve volunteered at the Spring Math Festival and Camp Lemma the past two years! I love talking with the kids who come because they often share math ideas or games that are new to me. Other times, I get to introduce them to something they keep thinking about even after the activity is over. Once, a kid was so excited about the math at my booth that he stayed there for the rest of the festival. I wanted to volunteer because proof- and puzzle-type problems like the ones at the festivals and Camp Lemma are what first got me interested in math in elementary school. I always hope that people come away having found a way of exploring math that they enjoy, whether that’s testing examples, turning math into art, or trying to prove statements.
Linda Green, PhD
What do the kids call you?
Linda
You’re clued into the recreational math community. What drives you to do this sort of outreach?
Outreach activities can foster kids' natural curiosity and joy, and reframe math as exploration and play. I love sharing my favorite puzzles and activities with others and seeing their excitement.