# Session Style: Try a Smaller Problem

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• Manipulatives (33)
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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)

### Fold & Cut

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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?

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

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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....

### Magic, Latin, & Sudoku Squares

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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

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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.

### Mathematical Games

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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...

### Pigeonhole Principle and Parity Problems

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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...

### Probability

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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...

### Recruiting Change for a Dollar

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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...

### Simplex Locks

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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?

### The Futurama Theorem

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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...