# Math Circle Activity Database

Search
Activity Authors
Activity Circles
Click To Sort By
Collections
Collections
• Teacher Math Circle Starter Activities (9)
• Math Circles of Inquiry (8)
• Student Math Circle Starter Activities (7)
• Math for Social Justice (5)
• Student Math Circle Full Classroom Activities (1)
Audience
• 1st - 2nd (12)
• 3rd - 5th (30)
• 6th - 8th (83)
• 9th - 12th (85)
• College Level (72)
• For Teachers (81)
Topics
Topics
• Algebra / Arithmetic (33)
• Combinatorics (31)
• Geometry (36)
• Mathematical Games (26)
• Mathematical Modeling (15)
• Number Theory (25)
• Parity / Invariants (2)
• Probability and Statistics (3)
• Problem Solving / General (39)
• Social Justice Mathematics (5)
Supporting Materials
Supporting Materials
• Facilitator Guides (88)
• Featured in MCircular (25)
• Handouts (38)
• Lesson Plan (10)
• Photos & Videos (28)
• References (36)
• Virtual Tools (17)
Session Styles
Session Styles
• Integrates Technology (17)
• Kinesthetic Element (11)
• Manipulatives (33)
• Multiple Representations (33)
• Problem Posing (45)
• Problem Sets (51)
• Try a Smaller Problem (40)
• Work Backwards (21)
Mathematical Practices
Mathematical Practices
• MP1 - Make sense of problems and persevere in solving them. (83)
• MP2 - Reason abstractly and quantitatively. (53)
• MP3 - Construct viable arguments and critique others' reasoning. (58)
• MP4 - Model with mathematics. (58)
• MP5 - Use appropriate tools strategically. (40)
• MP6 - Attend to precision. (40)
• MP7 - Look for and make use of structure. (72)
• MP8 - Look for and express regularity in repeated reasoning. (61)

### Gerrymandering

By:

Topic(s):

Supporting Resources:

Merriam Webster defines gerrymandering as “the practice of dividing or arranging a territorial unit into election districts in a way that gives one political party an unfair advantage in elections.” This activity tries to make sense of that definition using a few examples.

### Queen’s Move

By:

Topic(s):

Supporting Resources:

Students will explore a game between two players moving a chess Queen from place to place on a square grid. The Queen may move any number of spaces to the left, any number of spaces downward, and any number of spaces on the downward-left pointing diagonal. Each player takes turns...

### Primes!

By:

Topic(s):

Supporting Resources:

Mathematicians have long been fascinated by prime numbers and a great deal of number theory revolves around the study of primes. Develop a deeper understanding of these intriguing numbers by exploring the questions presented in this session.

### Good Things Come in Unexpected Packages

By:

Topic(s):

Supporting Resources:

“When my son opened his Christmas cracker, he discovered ‘The Mystery Calculator,’ a little two-player card game. Of course, I was intrigued and offered to exchange my fake mustache for his game. Little did I know where this gem of a gift would take me.” Exploring the math behind the...

### Hungry for Change: Food Deserts in CT

By:

Topic(s):

Supporting Resources:

In this lesson, we are tasked with determining a location for a new supermarket to address a possible “food desert” problem in Glastonbury. You will use these diagram to guide your analysis along with tools in Desmos and Geogebra. To qualify as “low access” in urban areas, at least 500...

### Measuring Up: “Perfect” Rulers

By:

Topic(s):

Supporting Resources:

Is it possible to measure all possible integer lengths on a ruler without marking every integer on that ruler? This is an engaging and challenging problem for all. Beautiful mathematics can be revealed while delving deeper into this seemingly easy question.

### Monty Hall Problem

By:

Topic(s):

Supporting Resources:

A prize is hidden behind one of three doors. You choose the door where you think the prize is hidden. But before the door is opened, one of the other 2 remaining doors is opened to reveal no prize. You can choose to keep the door you chose earlier or...

### Percents

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this module has students grapple with different representations of percents in various contexts in order to solve real life problems. Students need fluency in percentages for real world applications such as shopping, eating at restaurants, commission based careers, etc. Understanding...

### Introduction to Finite Systems: Z6 and Z7

By:

Topic(s):

Supporting Resources:

You are no doubt familiar with solving linear and quadratic equations with real numbers. However, in much the same way as learning Latin, French, or Spanish gives the language learner a better appreciation of English, so the careful examination of solution techniques in finite number systems adds depth to the...

### Catalan Numbers

By:

Topic(s):

Supporting Resources:

Suppose you have n pairs of parentheses and you would like to form valid groupings of them, how many groupings are there for each value of n? How many “mountain ranges” can you form with n upstrokes and n downstrokes that all stay above the original line? What about counting...

### The Mad Veterinarian on Mathematical Safari

By:

Topic(s):

Supporting Resources:

A Mad Veterinarian has created three animal transmogrifying machines…

While grappling with the posed questions, players will explore a set of problems, figuring out how and if the machines can complete a given transformation. Connections can be made to invariants, abstract algebra, graph theory, and Leavitt path algebra.

### The Game of SET

By:

Topic(s):

Supporting Resources:

SET is a fun game that can be enjoyed by kids as young as 6 and is challenging even for adults. It is rich in counting problems and is great for getting people to pose problems. It is also an example of a finite geometry and interesting to explore how...

### Fold & Cut

By:

Topic(s):

Supporting Resources:

What shapes can result from the following fold-and-cut process?
Take a piece of paper.
Fold it flat.
Make one complete straight cut.
Unfold the pieces.
Are all shapes possible?

### The 1-to-100 problem

By:

Topic(s):

Supporting Resources:

This exercise can be used for middle school students and older. The original problem seems almost impossibly difficult, but there are obviously many ways to approach it by considering simpler problems. As they investigate it, students are actually drilling their multiplication and addition facts. In addition, depending on how detailed...

### Tic-Tac-Toe 2.0

By:

Topic(s):

Supporting Resources:

The game of Tic-Tac-Toe has roots going back centuries. Grid-style game boards have been found in Ancient Egypt, during the Roman Empire, and in our current age on restaurant placemats. Multiple avenues of exploration are possible with this simple children’s game. A related game called “Gobblet Gobblers” takes Tic-Tac-Toe to...

### Simplex Locks

By:

Topic(s):

Supporting Resources:

A simplex lock is a type of combination door lock that involves pushing-in buttons. Given the set of rules for using a 5-button simplex lock, how many different combinations are there?

### Mondrian Art Puzzles

By:

Topic(s):

Supporting Resources:

You’re Mondrian’s mathematical boss. Instead of allowing Mondrian to randomly draw rectangles and colors -you lay out requirements: 1) Mondrian must cover an N by N canvas entirely with rectangles. 2) Every rectangle in the painting must have different dimensions. 3) Mondrian must use as few colors as possible, and...

### Squaring the Square

By:

Topic(s):

Supporting Resources:

Each puzzle is a rectangle made up completely of smaller squares. These squares have numbers inside that represents the length of their sides. Just knowing a few of the squares side lengths, can you figure out all the size of all the squares in the puzzle?

### Magic, Latin, & Sudoku Squares

By:

Topic(s):

Supporting Resources:

Squares and numbers, numbers and squares. There is something very satisfying about arranging numbers in a square formation, following specific rules, whether it is a Magic Square, Latin Square or Sudoku. This is probably why Sudoku puzzles are so popular. This session touches on some of the deep mathematics behind...

### Mathemagical Card Tricks

By:

Topic(s):

Supporting Resources:

There are many card tricks based on simple mathematics as opposed to sleight of hand. In this session, participants will play with a number of such tricks, test them out and work on discovering the math underneath, with a goal to formalize the mathematics that makes the trick work.

### Locked Out: A Breakout Box Session for Your Circle

By:

Topic(s):

Supporting Resources:

Escape Rooms and “Bomb Disposal” activities are growing in popularity as a form of team building and entertainment. This session blends the two ideas to create a cooperative math activity where the challenge is to solve math problems whose solutions generate combinations to open a locked box. The math problems...

### Mural Mathematics

By:

Topic(s):

Supporting Resources:

Students will explore existing equity themed murals to identify themes, and the mathematics necessary to plan/create a city mural. Students will utilize Google maps tools to begin connecting Mathematical representations to precisely interpret circle properties and apply them to the mural design.

### Place Value Problems

By:

Topic(s):

Supporting Resources:

In this session, we’ll learn how to solve problems related to place value. This is one of the fundamental concepts in arithmetic, something every elementary and middle school mathematics teacher should understand profoundly. Several example puzzles are followed by a rich selection of over 30 additional problems to explore. This...

### Knights and Knaves: A journey to the land of logic

By:

Topic(s):

Supporting Resources:

Logic provides the framework that allows us to agree on what is, or is not, a valid argument. It is possible to deepen understanding of the rules of logic by offering some well-chosen puzzles that highlight important ideas. This session’s puzzles all come from a lovely book entitled What is...

### System of Inequalities: Math Dance

By:

Topic(s):

Supporting Resources:

You want this year’s dance to be LIT! The dance committee has a goal of fundraising \$3,500 through ticket sales. How many tickets do they need to sell? Developed as part of the Math Circles of Inquiry project, this module presents an engaging problem which will allow students to investigate...

### Counterexamples

By:

Topic(s):

Supporting Resources:

What can you do with a paperclip? What can you do with a grid? Answers to these questions lead participants to explore their own conjectures. This professional development session will help everyone turn their classroom into a Thinking Classroom, where students use Conjectures and Counterexamples to power genuine mathematical experiences....

### Hyperbolic Footballs

By:

Topic(s):

Supporting Resources:

We are all familiar with the basic Euclidean geometry of the plane, including the behavior of parallel lines and angles in triangles. This familiarity may lead us to think it is a law of nature that parallel lines are always the same distance apart and the sum of the angles...

### Bubbling Cauldrons

By:

Topic(s):

Supporting Resources:

Place our numbers into the cauldrons in ascending order – you can choose which cauldron each one goes in. However, if two numbers in one cauldron add up to a third number in that same cauldron, they bubble up and cause an explosion! This means that all the numbers, leave...

### Skyscrapers

By:

Topic(s):

Supporting Resources:

Skyscrapers come in so many different sizes! Sometimes you can’t see small skyscrapers if tall ones are in front of them. Using clues about how many skyscrapers you can see from each side you look at them, can you figure out the layout of the entire city?

### Primes, Divisibility, and Modular Arithmetic

By:

Topic(s):

Supporting Resources:

Number theory is all about adding and multiplying integers: pretty simple stuff, good for elementary school or for PhD mathematicians. Dr. Arnold Ross says of number theory, that the purpose is “to think deeply of simple things.” So let’s do that together. This session includes multiple problem sets beginning with...

### Racial Profiling

By:

Topic(s):

Supporting Resources:

To investigate situations in the real world, we sometimes create a mathematical model. A mathematical model is a simplified version of the real world that allows us to understand the real world a little better. Over time we can change this model so that it gets closer and closer to...

### Can Voting Ever Really Be “Fair”?

By:

Topic(s):

Supporting Resources:

What is “fair” when voting? In this session, the participants apply and analyze several established methods for determining the “voice” of the majority. They will discover these methods through an inquiry-based experience in a deep problem, and join an ongoing discussion that has gone on for hundreds of years about...

### Supreme Court Handshakes

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this session is a good introduction to the 8th grade or Algebra Math curriculum using inquiry based instruction. Students are asked to use their problem solving skills in order to determine the relationship between the number of Supreme Court justices...

### Game of Criss-Cross

By:

Topic(s):

Supporting Resources:

The purpose for having students play the game of Criss-Cross is to motivate them to explain the underlying mathematical reason governing who wins or loses. This exploration should lead the students to form, test, and ultimately prove conjectures about how to win at Criss-Cross. The game illustrates a beautiful application...

### Wolves and Sheep

By:

Topic(s):

Supporting Resources:

The rules are simple: you want to place the sheep on the board so that the wolves can’t eat them. A wolf can eat a sheep if it has a direct path to it – or is in same row, column, or diagonal as that sheep. Can you place all...

By:

Topic(s):

Supporting Resources:

Quilts are a familiar set of cultural artifacts for many people. Quilts also happen to be beautifully mathematical. “What sorts of symmetries can a quilt block possess?” Participants will design and examine quilt blocks, and develop a taxonomy of symmetry in order to compare the blocks according to the symmetries,...

### The Roommate Game: An Exploration of Stable Matchings

By:

Topic(s):

Supporting Resources:

College students need to be matched with a roommate. They each make a list of who they prefer to room with. Given the preference lists for each individual, can we find a matching that is stable? That is, would any pair ask to change rooms because they would rather room...

### Semiregular Tilings

By:

Topic(s):

Supporting Resources:

Can you find all possible semiregular tilings of the plane? A tiling of the plane covers the (infinite) plane, without gaps or overlaps, using congruent copies of one or more shapes. A semiregular tiling is a tiling of the plane with certain constraints: two or more regular polygons are used,...

### Trigonometric Ratios in Right Triangles

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this five to six day activity is designed to help students understand trigonometric ratios, by building on their understanding of similar triangles and ratios of corresponding sides. The purpose of this module is for students to spend time and energy...

By:

Topic(s):

Supporting Resources:

The divisibility rules are often “accepted without proof” by both teachers and students. The problem explored in this session involves a rich, novel way of looking at “amazing numbers,” to authentically develop notions around patterns of divisibility as a solution strategy. “This session offered opportunities for the group to use...

### Match or No Match

By:

Topic(s):

Supporting Resources:

In this session, participants will explore the Match-No Match game: two players each draw one chip out of a bag – if the color of the chips match Player 1 wins, if not Player 2 wins. Under what conditions is this a fair game? How do we know? How can...

### Modeling a Pandemic

By:

Topic(s):

Supporting Resources:

How can mathematics help us understand the phenomenon of a pandemic? What factors impact the spread of a disease like Covid-19? Which of these factors can we influence? (society, in schools) How can mathematics help us act during a pandemic toward better outcomes?

### Codes, Ciphers, and Secrets

By:

Topic(s):

Supporting Resources:

Cryptography is the study and practice of secure communication, making it an interesting and relevant application. In addition to number theory concepts like modular arithmetic, this session uses locks, codes, and ciphers to explore functions (definition, inverse functions, linear functions).

### Folding Perfect Thirds

By:

Topic(s):

Supporting Resources:

Imagine you’re packing for a trip, and you’re planning on bringing your favorite tie. It’s too long to fit in your suitcase, even after folding it in half. You would fold it into fourths, but you don’t want all of those creases ruining your tie. You’ve decided folding it into...

### Conway’s Rational Tangles

By:

Topic(s):

Supporting Resources:

What do adding positive and negative fractions have to do with tying knots? In this entertaining lesson, students will use ropes to explore and identify mathematical operations that untangle knots and lead to new thinking. Simple operations of twists and rotations circle back to practicing the addition of positive and...

### Probability

By:

Topic(s):

Supporting Resources:

Some probability problems can be solved by drawing a picture; this approach is sometimes called geometric probability. Other approaches can include experimentation, looking at smaller cases, looking at extreme cases, recursion, or carefully listing possibilities. This session includes ten problems that can be explored alone or in sets, providing material...

### Mathematical Magic for Muggles

By:

Topic(s):

Supporting Resources:

Presented are several easy-to-perform feats that suggest supernatural powers such as telepathy, “seeing fingers,” predicting the future, photographic memory, etc. Each trick uses simple mathematical ideas that allow information to flow effortlessly and sneakily, among them simple, efficient “coding” parity and other invariants symmetry probability One can approach these activities...

### Factor Game

By:

Topic(s):

Supporting Resources:

A teacher challenges students to a game. The rules are explained as the game progresses. The player with the highest total wins! Students then play against each other. Afterwards, while analyzing the game, prime, composite, perfect, deficient, and abundant numbers are discovered and defined. Students again play the game using...

### Winning the Lottery, An Expected Value Mystery

By:

Topic(s):

Supporting Resources:

In 2005, while researching the expected value for lottery tickets in various states, a group of MIT students won millions of dollars in the Massachusetts \$2 Cash Winfall drawing. Do you want to know how they did it? This teacher led activity starts with a lottery, explores expected value, and...

### Pigeonhole Principle and Parity Problems

By:

Topic(s):

Supporting Resources:

The pigeonhole principle states that if n pigeons are put into m cubbies, with n > m, then at least one cubby must contain more than one pigeon. Parity problems deal with odd and even integers. Here is a collection of problems that can be used in a single problem...

### Solving Linear Equations: An M&M Mystery

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this session is aimed at grades 7 or 8, but may be useful for high school algebra. It consists of worksheets and series of videos meant to get students to develop an understanding of solving linear equations, using the real...

### I See Platonic solids In Your Future

By:

Topic(s):

Supporting Resources:

What is the three-dimensional shape inside the classic Mattel Magic 8-Ball toy? This hands-on activity explores the intriguing fact that there are only five different types of Platonic solids, whereas there are infinitely many regular polygons.

This session is also suitable for student math circles or the classroom.

### Coins in Twoland

By:

Topic(s):

Supporting Resources:

In Twoland, the only money is coins with value 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, and so on. How many ways can change be given, following Twoland’s strict rules? In this whimsical session, participants will practice precision and organizational skills. This session is also suitable...

### Tiling With Pentagons

By:

Topic(s):

Supporting Resources:

A pentagonal tiling is a tiling of the plane where each individual piece is in the shape of a pentagon. The plane cannot be tiled with regular pentagons. However, are there any convex pentagons that can tile the plane? This session explores various pentagons and their tiling abilities. From 1918...

### Piece of Cake; Delectable Fractions and Decimals

By:

Topic(s):

Supporting Resources:

While exploring the relationship between fractions and decimals, participants will have the opportunity to practice operations with fractions, notice and explain patterns, review understandings of place value and number sense, and justify their reasoning. You can get a taste of math research by repeating these two steps: Think about an...

### Prejudiced Polygons

By:

Topic(s):

Supporting Resources:

We adapt “Parable of the Polygons” (Vi Hart and Nicky Case), an online simulation on diversity and segregation, into an appropriate MTC session. The session is interactive, and offers multiple layers of content depending on the age and comfort level of students with conversations on social issues. These levels include:...

### Euler Characteristic Exploration

By:

Topic(s):

Supporting Resources:

The purpose of this activity is to introduce students to elementary concepts in graph theory in a hands-on, accessible manner. Students will create their own graphs, count certain quantities related to their graphs, make conjectures regarding these quantities, and learn how to explain why their conjecture is true. In the...

### One, Two, Three, Four: Building Numbers with Four Operations

By:

Topic(s):

Supporting Resources:

What numbers can you make with 1, 2, 3, and 4, using the operations of addition, subtraction, and multiplication? Work on these problems builds arithmetic fluency and provides opportunities to identify patterns, develop and defend arguments, and create conjectures. This investigation also highlights how thin the boundary is between a...

### Mathematical Games

By:

Topic(s):

Supporting Resources:

This session includes 15 games using manipulatives or paper and pencil. The goal is to decide which one of the two players has a winning strategy. To solve a game means to find a winning, or a non-losing, strategy for one of the players. An answer must include a detailed...

### Pick’s Theorem

By:

Topic(s):

Supporting Resources:

Austrian mathematician Georg Pick first stated this theorem in 1899. However it wasn’t brought to broad attention until 1969. In this exploration, participants will use rates of change to aid them in discovering Pick’s famous formula by finding a relationship between the area of the figure, the number of perimeter...

### Rational Numbers

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this module is an introductory activity for rational numbers, likely aligned with Grade 7. Students will be given five points on a number line and will be asked to estimate the values of each in a 3-part task and explain...

### Art Meets Math: Escher’s Tilings

By:

Topic(s):

Supporting Resources:

Dutch artist M. C. Escher is well known for his amazing prints of interlocking lizards, fish transforming into birds, and angels and devils intertwined, just to name a few. His intricate tilings offer a beautiful and engaging way to explore ideas related to geometric transformations and symmetries.

### Getting Started with PROBLEM SOLVING: A Trio of Friendly Problems

By:

Topic(s):

Supporting Resources:

The three problems presented for this extended lesson have both individual and cluster appeal. Since each of these problems can be visualized or acted out quite readily, the problems can be accessible at some level for virtually every middle school student. By offering all three of the problems to your...

By:

Topic(s):

Supporting Resources:

For the Math Mind Reading Trick, you’ll need a volunteer who’s willing to have their mind read. The person performing the trick holds out the four cards and askes their volunteer to pick a number (whole numbers only, no fractions allowed!) between 1 and 15 and keep it a secret....

### Bicycle Math

By:

Topic(s):

Supporting Resources:

You are brought to a crime scene. You are told that a thief just made off with a bag full of diamonds, escaping on a bicycle. You come across a pair of bicycle tracks in the snow, no doubt made by the fleeing thief. But which way did the thief...

### Balance Beans

By:

Topic(s):

Supporting Resources:

If you start with some beans on a seesaw and you’re given certain additional beans to place on the seesaw, can you do it so the seesaw balances? In this activity, students start by trying to solve various challenges involving different arrangements of beans on the seesaw and then design...

### Acting Out Mathematics

By:

Topic(s):

Supporting Resources:

In teams, participants will create body movements related to geometry facts and will use their body to create a convincing argument as to why the statement is true. Please bring your fun-meter, your creativity, your body, and open physical space (for moving) to this session.

### Shifting Gears: Approximations in Cycling

By:

Topic(s):

Supporting Resources:

After studying James Tanton’s MTC session about bicycle tracks, avid bicyclist Michael Nakamaye started questioning the mathematics behind how a bike works.

How do gears work? How many teeth are there usually on the different gears? Why? How is a bike like a ratio machine?

### Liar’s Bingo

By:

Topic(s):

Supporting Resources:

From recognizing a pattern to generating terms, to abstracting and making inferences, tasks based on patterns embody the “low-threshold, high-ceiling” trait of good problems. Liar’s Bingo is all about patterns. This session involves recognizing patterns and searching for underlying structure, number theory, numeration, and potentially binary arithmetic. Sometimes, as in...

### Function Diagrams

By:

Topic(s):

Supporting Resources:

What if we graphed with parallel axes instead of perpendicular ones? This intriguing transformation exchanges points and lines; replacing points being on the same line, with lines passing through the same point. By changing the way we usually graph functions, new patterns and deeper understandings can emerge.

### Count Me In

By:

Topic(s):

Supporting Resources:

Counting problems can involve the counting of combinations, permutations, factorials, pathways using Pascal’s Triangle, partitions and complements, and many more. In this lesson many different types of counting problems (some easy and some harder) were given to groups of teachers to solve in whatever way they preferred.

### Introduction to Diophantine Equations

By:

Topic(s):

Supporting Resources:

Diophantine equation – an equation whose roots are required to be integers. In this article we will only touch on a few tiny parts of the field of linear Diophantine equations. Some of the tools introduced, however, will be useful in many other parts of the subject. Suppose that dolls...

### Grid Power

By:

Topic(s):

Supporting Resources:

“When I grew up in the Soviet Union, all we used for math was grid paper. Grid paper leads to discovery.” This is how Tatiana Shubin, San Jose State University, begins her lesson demonstrating the myriad of wonderful math questions arising from a simple sheet of grid paper. Attempting to...

### Daydreams in Music: Patterns in Musical Scales

By:

Topic(s):

Supporting Resources:

There is no shortage of examples of mathematicians and scientists who are also musicians. Perhaps it is the abundance of patterns and structure prevalent in music that underpin these common interests. This exploration of musical scales is an engaging session, accessible to elementary and secondary teachers with and without a...

### The Dollar Game

By:

Topic(s):

Supporting Resources:

A group of people, some that just met, have a dilemma. Some people owe money and some have money. Problem is that only people that know each other, connected by nodes, can give or lend a dollar. But they must give each person they know a dollar, even if that...

### The Jug Band

By:

Topic(s):

Supporting Resources:

“Using just that 5 pint jug and that there 12 pint jug, measure me 1 pint of water!” Is this possible with just the two jugs? What about a 7 pint jug and 17 pint jug? Or p pint and q pint jugs?

### The Futurama Theorem

By:

Topic(s):

Supporting Resources:

In the television show Futurama, Professor Farnsworth and Amy decide to try out their newly finished “Mind-Switcher” invention on themselves. When they try to switch back, they discover a key flaw in the machine’s design: it will not allow the same pair of bodies to be used in the machine...

### Puppies & Kittens

By:

Topic(s):

Supporting Resources:

A local animal shelter has a puppies and kittens available for adoption that you just happen to be itching to own! In this week’s “paw-some” activity, two players begin with a certain number of animals to choose from and take turns adopting animals. The player to adopt the last animal...

### How do you connect the dots?

By:

Topic(s):

Supporting Resources:

Suppose you have a collection of dots on a page and want to find a way to connect them “automatically” in some meaningful way. How would you do it? This question has inspired mathematicians, computer scientists, statisticians, network engineers, and even artists and architects! We will learn about the exciting...

### Lockers: An Open-and-Shut Case

By:

Topic(s):

Supporting Resources:

A classic Math Circle problem! At a large high school, there are 10000 lockers. The lockers are numbered, in order, 1, 2, 3, . . . , 10000, and to start, each locker is closed. There are also 10000 students, also numbered 1, 2, 3, . . . , 10000....

### Visualization in Algebra

By:

Topic(s):

Supporting Resources:

Many topics in mathematics can be made much clearer when symmetric aspects are made clear or when nice alternative visualizations are possible. When this occurs, it helps both the student and the teacher. We will examine visualization and symmetry in a very general way by means of a set of...

### Cup Stacking

By:

Topic(s):

Supporting Resources:

Begin with a row of cups and end with all of the cups in a single stack. Rules: 1. Count the number of cups in a stack. That stack must jump that number of spaces. For example, 1 cup can only move 1 space; 2 cups have to move 2...

### Intersection Math

By:

Topic(s):

Supporting Resources:

What is four times three? 12 you might say, but no longer! In a new type of math — intersection math— we will see that four times three is 18, two times two is 1, and that two times five is 10 (Hang on! That’s not new!) Let’s spend some...

### I Walk the Line

By:

Topic(s):

Supporting Resources:

Your regular commute begins at your house and ends at your office at the corner of 5th street and 6th avenue. You have been making this trip for years, but you are the restless (or adventurous) type, and you try to take a different route each day. At some point,...

### Can you “Spot it!”

By:

Topic(s):

Supporting Resources:

Spot It! is a matching game for kids but the mathematics behind the game is both deep and accessible. This session is an open ended investigation of the game where participants discover the hidden structures, patterns, and formulas that make the game special. It is particularly interesting to see how...

### A Problem Fit for a Princess: Apollonian Gaskets in History

By:

Topic(s):

Supporting Resources:

The examination of an MTC logo takes us on a journey starting over 2,000 years ago in ancient Greece, passing through seventeenth century Bohemia, moving through twentieth century fractals, and ultimately forming the focus of this problem-solving session. Explore the Circles of Apollonius, the question posed by Princess Elisabeth of...

### Systems of Linear Equations

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, this short module explores a graphical solution to a system of equations. Students answer questions about lemonade sales and physically stand on the coordinates of a giant grid in order to see that plotting two equations on the same set...

### Flipping Pancakes

By:

Topic(s):

Supporting Resources:

The Pancake Problem, first posed in 1975, is a sorting problem with connections to computer science and DNA rearrangements, which leads to discussions of algorithms, sequences, and the usefulness of approximations and bounds. The original problem was first posed by mathematician Jacob Goodman under the pen name “Harry Dweighter” (read...

### Recruiting Change for a Dollar

By:

Topic(s):

Supporting Resources:

How many different ways are there to make change for a dollar? As mathematicians we often search for patterns in a problem. However, for this problem, there is no simple, predictable pattern to build to an answer, encouraging participants to reach outside their comfort zones and ponder alternative strategies in...

### Puzzles, Bands, and Knots

By:

Topic(s):

Supporting Resources:

This activity packed session starts with a fun Pythagorean Puzzle Proof. Then, Knot Theory is explored while experimenting with the Mobius Band, Knots and Links; Untangling Ropes and Rings, and acting out the Human Knot Experiment. These explorations are further connected to the coiling and knotting of DNA molecules. These...

### Big Numbers

By:

Topic(s):

Supporting Resources:

Using the standard arithmetic operations (addition, subtraction, multiplication, division and exponentiation), what is the largest number you can make using three copies of the digit “9”? While this would be a pretty large number, with a little cleverness you can do far better. This session explores VERY large numbers!

### Animated Activities

By:

Topic(s):

Supporting Resources:

In this session, we introduce participants to the programming language, Scratch, by giving them a rich task. As they explore possible approaches to achieving the goals of the task, they naturally uncover the three fundamental structures of programming (conditionals, loops, and sequential statements). We explore multiple approaches to the task,...

### Humans, Zombies, & Other Problems Crossing the River

By:

Topic(s):

Supporting Resources:

A town faces an epidemic of zombies! Luckily, the virus has just started to spread and the infected are able to stave off their hunger for human brains… for now. In fact, they’re willing to work alongside the remaining humans to help them get across a river to safety. Can...

### Coloring

By:

Topic(s):

Supporting Resources:

Consider a 9 × 9 chessboard, and you wish to cover as much of it as possible using figures shaped like the one to the right, where each of the four squares is the same size as the squares on a chessboard. The pieces can be rotated or flipped over....

### Practical Probability: Casino Odds and Sucker Bets

By:

Topic(s):

Supporting Resources:

Gambling casinos are there to make money, so in almost every instance, the games you can bet on will, in the long run, make money for the casino. However, to make people gamble, it is to the casino’s advantage to make the bets appear to be “fair bets,” or even...

### KenKen

By:

Topic(s):

Supporting Resources:

Kenken is a puzzle whose solution requires a combination of logic and simple arithmetic skills. The puzzles range in difficulty from very simple to incredibly difficult. Students who get hooked on the puzzle will be forced to drill their simple addition, subtraction, multiplication and division facts.

### Touching Infinity: Hyperbinary Numbers and Fraction Trees

By:

Topic(s):

Supporting Resources:

Are there more fractions than counting numbers? Surprisingly, an investigation into binary notation can help us answer this question! This session explores the binary number system. Participants will investigate Hyperbinary numbers, create a Fraction Tree, and discover connections between them.

### Intergenerational Wealth

By:

Topic(s):

Supporting Resources:

Students will gather data on median household incomes from three towns across Connecticut (including their own town) and will calculate potential future wealth using exponential modeling. Students will compare outcomes of these models and discover factors that impact a household’s ability to accumulate and transfer wealth. Students will understand the...

### Hercules and the Hydra

By:

Topic(s):

Supporting Resources:

After a late night reading about classical mythology (or watching “Clash of the Titans” yet again), you drift off to sleep and dream that you are face-to-face with a many-headed monster that is clearly not happy to see you, either. “Ahah,” you think, “I must be Hercules and that ....

### Optimal Locations of Firehouses (Taxi-cab Metric)

By:

Topic(s):

Supporting Resources:

This session asks participants to expand their notion of “distance,” using a nontraditional taxicab metric instead of the usual Pythagorean notion. Participants are guided to construct the equivalent of “circles” with this new metric and to look at the intersections of multiple such circles. In particular, two firehouses in Gridtown...

### Making Connections Between Forms of Quadratic Equations

By:

Topic(s):

Supporting Resources:

Developed as part of the Math Circles of Inquiry project, the goal of this module is to help students in Algebra II become fluent in the various forms of a parabola equation based on the information that they are given. Students sometimes fail to understand that there are multiple ways...