Skit: The Handshake Problem

The handshake problem

If seven people meet at a party, and each person shakes the hand of everyone else exactly once, how many handshakes are there in all?

Our homeschool co-op held an end-of-semester assembly. Each class was supposed to demonstrate something they had learned.

I threatened to hand out a ten question pop quiz on integer arithmetic, but instead my pre-algebra students presented this skit.

Download a Printable Script

Cast

1-3 narrators (or more, if you have a large group)
7 friends (non-speaking parts, adjust to fit your group)

Props

Each friend will need a sheet of paper with a number written on it big and bold enough to be read by the audience. The numbers needed are 0, 1, 2, 3, … up to one less than the number of friends. Each friend keeps his paper in a pocket until needed.

Continue reading Skit: The Handshake Problem

Math Journal: The 1-2-3 Puzzle

colorful numbers 1, 2, 3

Math Journaling Adventures series by Denise GaskinsThere’s still time to check out my Math Journaling Adventures project and discover how playful writing activities will help your students learn mathematics. Preorder your books today!

Meanwhile, here’s a math puzzle to share with your kids…

Write down any whole number. It can be a single-digit number, or as big as you like. For example:

64,861,287,124,425,928

Now, count up the number of even digits (including zeros), the number of odd digits, and the total number of digits your number contains. Write those counted numbers down in order, like this:

64,861,287,124,425,928
even 12, odd 5, total 17

Continue reading Math Journal: The 1-2-3 Puzzle

Memories: The Oral Story Problem Game

photo of sheep in a field

Homeschool Memories…

Perhaps you’ve heard me mention the oral story problem game. It was one of my favorite ways to get my children thinking about math, back in our early days of homeschooling. We played in the car on the way to soccer practice, or while we washed dishes, or sitting in the lobby waiting for a doctor’s appointment.

The rules are simple: I’ll make up a math problem for you to solve. And then you make up one for me.

The kids always loved trying to stump me.

This problem from Henry Ernest Dudeney’s Amusements in Mathematics reminded me of those days. This is exactly the way my eldest loved to torture me…

Continue reading Memories: The Oral Story Problem Game

Puzzle: Henry Dudeney’s Pebble Game

photo of girl playing with pebbles on the beach

English mathematician and puzzle-meister Henry Ernest Dudeney once wrote:

“It may be said generally that a game is a contest of skill for two or more persons, into which we enter either for amusement or to win a prize. A puzzle is something to be done or solved by the individual.

    “The example that I give here is apparently a game, but, as in every case one player may win if he only play correctly, it is in reality a puzzle. The interest, therefore, lies in attempting to discover the leading method of play.”

    Below is the puzzle game as Dudeney explained it.

    Play it for fun at first, then see if you can solve the puzzle.

    Continue reading Puzzle: Henry Dudeney’s Pebble Game

    Can You Solve It? The Cyclists’ Feast

    English mathematician Henry Ernest Dudeney wrote logic puzzles and mathematical games for several newspapers and magazines, later collected into books. This poem is from Amusements in Mathematics, published by Thomas Nelson and Sons, 1917.

    The numbers are simple enough that younger students can solve it by the guess-and-check method. Older students or adults may want to set up a quadratic equation.

    Historical Note: In the British currency of the time, there were 12 pennies to a shilling and 20 shillings to a pound (which was also called a sovereign).

    The Cyclists’ Feast

    ’Twas last Bank Holiday, so I’ve been told,
    Some cyclists rode abroad in glorious weather.
    Resting at noon within a tavern old,
    They all agreed to have a feast together.

    “Put it all in one bill, mine host,” they said,
    “For everyone an equal share will pay.”
    The bill was promptly on the table laid,
    And four pounds was the reckoning that day.

    But, sad to state, when they prepared to square,
    ’Twas found that two had sneaked outside and fled.
    So, for two shillings more than his due share
    Each honest friend who had remained was bled.

    They settled later with those rogues, no doubt.
    How many were they when they first set out?

    Did You Solve It?

    One fun thing about math is that you really don’t need the answer book. You can always check the math for yourself: Does your answer make sense? Does it fit the story?

    Would you like to write a math poem puzzle of your own? I’d love to hear it!

     
    * * *

    For more ideas on writing math poetry, check out Math Makers: Write a Poem.

    This blog is reader-supported.

    If you’d like to help fund the blog on an on-going basis, then please join me on Patreon for mathy inspiration, tips, and an ever-growing archive of printable activities.

    If you liked this post, and want to show your one-time appreciation, the place to do that is PayPal: paypal.me/DeniseGaskinsMath. If you go that route, please include your email address in the notes section, so I can say thank you.

    Which I am going to say right now. Thank you!

    “Can You Solve It? The Cyclists’ Feast” copyright © 2023 by Denise Gaskins. Image at the top of the post copyright © yanlev / Depositphotos.

    Celebrating Math with Pi Day

    Are your students doing anything special for Pi Day?

    Back when we were homeschooling, my kids and I always felt stir-crazy after two months with no significant break. We needed a day off — and what better way could we spend it than to play math all afternoon?

    I love any excuse to celebrate math!

    Pi Day is March 14. If you write dates in the month/date format, then 3/14 at 1:59 is about as close as the calendar can get to 3.14159etc.

    (Otherwise, you can celebrate Pi Approximation Day on July 22, or 22/7.)

    Unfortunately, most of the activities on teacher blogs and Pinterest focus on the pi/pie wordplay or on memorizing the digits. With a bit of digging, however, I found a few puzzles that let us sink our metaphorical teeth into real mathematical meat.

    What’s the Big Deal? Why Pi?

    In math, symmetry is beautiful, and the most completely symmetric object in the (Euclidean) mathematical plane is the circle. No matter how you turn it, expand it, or shrink it, the circle remains essentially the same.

    Every circle you can imagine is the exact image of every other circle there is.

    This is not true of other shapes. A rectangle may be short or tall. An ellipse may be fat or slim. A triangle may be squat, or stand upright, or lean off at a drunken angle. But circles are all the same, except for magnification. A circle three inches across is a perfect, point-for-point copy of a circle three miles across, or three millimeters.

    What makes a circle so special and beautiful? Any child will tell you, what makes a circle is its roundness. Perfectly smooth and plump, but not too fat.

    The definition of a circle is “all the points at a certain distance from the center.” Can you see why this definition forces absolute symmetry, with no pointy sides or bumped-out curves?

    One way to express that perfect roundness in numbers is to compare it to the distance across. How many times would you have to walk back and forth across the middle of the circle to make the same distance as one trip around?

    The ratio is the same for every circle, no matter which direction you walk.

    That’s pi!

    Puzzles with Pi

    For all ages:

    Sarah Carter created this fun variation on the classic Four 4s puzzle for Pi Day:

    Using only the digits 3, 1, 4 once in each calculation, how many numbers can you make?

    You can use any math you know: add, subtract, multiply, square roots, factorials, etc. You can concatenate the digits, putting them together to make a two-digit or three-digit number.

    For older students:

    1. Imagine the Earth as a perfect sphere with a long rope tightly wrapped around the equator. Then increase the length of the rope by 10 feet, and magically lift it off the Earth to float above the equator. Will an ant be able to squeeze under the rope without touching it? What about a cat? A person?

    2. If you ride a bicycle over a puddle of water, the wheels will leave wet marks on the road. Obviously, each wheel leaves a periodic pattern. How the two patterns are related? Do they overlap? Does their relative position depend on the length of the puddle? The bicycle? The size of the wheels?

    3. Draw a semicircle. Along its diameter draw smaller semicircles (not necessarily the same size) that touch each other. Because there are no spaces in between, the sum of the diameters of the small semicircles must equal the diameter of the large one. What about their perimeter, the sum of their arc lengths?

    4. Choose any smallish number N. How can you cut a circular shape into N parts of equal area with lines of equal lengths, using only a straight-edge and compass? Hint: The lines don’t have to be straight.

    [Solutions at Alexander Bogomolny’s Pi Page. Scroll down to “Extras.”]

    It can be of no practical use to know that Pi is irrational, but if we can know, it surely would be intolerable not to know.

    — Edward Titchmarsh

    For More Information

    Here are a few pi-related links you may find interesting:

    Or for pure silliness:

    Have fun playing math with your kids!

    John Reid, CC BY-SA 3.0 via Wikimedia Commons

    Playful Math: Getting Students To Write Their Own

    To wrap up our week of exploring the resources from Word Problems from Literature, let’s talk about getting students to write their own math.

    Check in on the Kickstarter

    First up, I’m sharing an excerpt from the Word Problems Student Workbook. The “Story Problem Challenge” is one of my favorite math club activities.

    Following that, you’ll find an amazing online mathemagical adventure for middle school: The Arithmetiquities. It’s great fun, and a great inspiration for students to create their own math stories.

    Have fun writing math with your kids!

    The Story Problem Challenge

    What do you get when you cross a library book or favorite movie with a math worksheet? A great alternative to math homework!

    The rules are simple:

    (1) Choose a worksheet calculation to be the basis for your word problem.

    (2) Solve the calculation.

    (3) Consider where these numbers could make sense in your book or movie universe. How might the characters use math? What sort of things would they count or measure? Do they use money? Do they build things, or cook meals, or make crafts? Do they need to keep track of how far they have traveled? Or how long it takes to get there?

    (4) Write your story problem.

    To make the game easier, you may change the numbers to make a more realistic problem. But you must keep the same type of calculation. For example, if your worksheet problem was 18÷3, you could change it to 18÷6 or 24÷3 or even 119÷17 to fit your story, but you can’t make it something like 18−3.

    Remember that some quantities are discrete and countable, such as hobbits and fireworks. Other quantities are continuous, such as a barrel of wine or a length of fabric. Be sure to consider both types when you are deciding what to use in your problem.

    Then share your problem with friends, and you try their problems. Can you stump each other?

    A Note about Copyright and Trademarks

    Old books are in the public domain, so you can always use characters like Robin Hood, Sherlock Holmes, or Winnie-the-Pooh (but not the newer Disney version with the red jacket). But most books and movies are the protected intellectual property of their authors or estates, or of the company who bought those rights.

    When you write problems for your own private use, feel free to use your favorite characters from any story. That’s like fan fiction, secret, just for your own pleasure.

    But if you decide to share your creation beyond your own home or classroom, then be sure to “genericize” it first. Change or remove the proper names, using general descriptions instead.

    For example, if you love the Harry Potter series, you might want to use Harry or Hermione in your story problems. Instead, write about “the boy wizard destined to fight an evil sorcerer.” Or “the bright young witch who can master any spell.”

    Or if you like the Star Wars movies, you might write about “an interstellar justice warrior with an energy sword.” Or “an alien master of martial arts training a cocky but inexperienced apprentice.”

    The Arithmetiquities

    When the world of Sfera is threatened by the machinations of a malevolent sorcerer, it will be up to a band of unlikely heroes to become the brightest light in the darkness.

    The adventurers fan out across the land to find and retrieve the Arithmetiquities, a set of ancient mathemagical artifacts.

    The Arithmetiquities is a fantasy adventure story told through a sequence of 36 mathematical puzzles.

    Join the Adventure

    “Though it is still before sunrise, Lumparland Harbor is already bustling. Sailing ships moor at the misty docks, bringing travelers and goods to the seaside town. Three dwarves disembark from different ships, each adventurer returning home from some faraway locale. The three women gather at the end of the pier.

      “The strangers discover that they all live along the main road that leads from the harbor, so they decide to split the cost of a wagon. Egga lives 10 miles away, Floora lives 20 miles away, and Greeta lives 30 miles away. The wagon ride costs $1.50 per mile regardless of the number of passengers.

        “How much should each of the adventurers pay so that each one has a fair fare?”

        —Jason Ermer, “Lumparland Harbor,” The Arithmetiquities Chapter I

         
        * * *

        Are you looking for more creative ways to play math with your kids? Check out all my books, printable activities, and cool mathy merch at Denise Gaskins’ Playful Math Store. Or join my email newsletter.

        This blog is reader-supported. If you’d like to help fund the blog on an ongoing basis, then please join me on Patreon (or choose the paid level on Substack) for mathy inspiration, tips, and an ever-growing archive of printable activities.

        “Playful Math: Getting Students To Write Their Own” copyright © 2022 by Denise Gaskins. Image at the top of the post copyright © Hannah Olinger via Unsplash.com.

        Problem Solving with James Tanton

        At the back of my new Word Problems from Literature book, I’ve included an appendix with links to recommended online resources.

        Buy It Now

        So I thought this week, I’d share some of my favorites with you. First up: Problem Solving Tips from James Tanton.

        You may know Tanton from the popular Exploding Dots and other activities at the Global Math Project website. But he’s been busy for decades sharing the delight and the beauty of the subject. He currently serves as the Mathematician-at-Large for the Mathematical Association of America.

        Read on to discover several of Tanton’s best problem-solving tips for middle school and older students.

        Have fun exploring math with your kids!

        How to Think like a School Math Genius

        In this 4-video series, Tanton presents five key principles for brilliant mathematical thinking, along with loads and loads of examples to explain what he means by each of them. He says it’s “a call for parents and teachers to be mindful of the life thinking we should foster, encourage, promote, embrace and reward — even in a math class!”

        Watch the Videos:

        Two Key — but Ignored —Steps to Solving Any Math Problem

        How many degrees in a Martian circle?
        Every challenge or problem we encounter in mathematics (or life!) elicits a human response. The dryness of textbooks and worksheets in the school world might suggest otherwise, but connecting with one’s emotions is fundamental and vital for success — and of course, joy — in doing mathematics.

        Read the Article

        MAA AMC Curriculum Inspirations

        Essays and videos showing how to approach math puzzles in a way that a) is relevant and connected to the curriculum, and b) revels in deep, joyous, mulling and flailing, reflection, intellectual play and extension, insight, and grand mathematical delight.

        Scroll down and start with the Ten Problem-Solving Strategies.

        Download the Puzzles

        Think Puzzles and Think Cool Math

        Here are some essays illustrating astounding tidbits of mathematical delight. And here are some purely visual puzzles to surprise.

        Explore and Enjoy

        “The true joy in mathematics, the true hook that compels mathematicians to devote their careers to the subject, comes from a sense of boundless wonder induced by the subject.

          “There is transcendental beauty, there are deep and intriguing connections, there are surprises and rewards, and there is play and creativity.

            “Mathematics has very little to do with crunching numbers. Mathematics is a landscape of ideas and wonders.”

            —James Tanton

            CREDITS: Feature photo (top) by Ian Stauffer via Unsplash.com.

            Playful Math Journaling with a Cat

            As queen of the house, Cimorene insists on being involved in anything that happens in her domain. This includes promoting the Playful Math Journaling Kickstarter.

            So she created a cat math journaling prompt to help your children experience the fun of playing around with math.

            But first, she encourages you to visit the Kickstarter page and download the free 16-page printable Math Journaling Sampler file. Your kids will love solving Cimorene’s puzzle on one of the parchment-style pages!


            [The free download will always be there, even after the Kickstarter project ends.]
            Visit the Kickstarter

            Here is Cimorene’s Puzzle

            “The Princess of Cats has a luxuriously soft tail about 12 inches (30 cm) long. Her tail is three times the length of her noble head. Her beautiful, furry body is as long as head and tail together. How long is the Princess from her delicate nose to the tip of her majestic tail?”

            So, how does math journaling work? What do children do with a problem like this?

            They may want to make a list of the things they know from the story. Perhaps they will draw a picture of the cat and label the proportions. Each will take their own approach to figure it out.

            And then the best part of any math journal prompt is when kids make their own math.

            • Can they write a new puzzle about their own pet?
            • Or about their favorite animal?

            Encourage your children to share their math creations with their friends and family.

            Cimorene would love to read it, too! If you share your story in the comments section below, I will be sure to show it to her.

            And remember to back the Playful Math Journaling Kickstarter so your whole family can enjoy the adventure of playing with math!

            Math Puzzle from the Ancient Kingdom of Cats

            It may look like Cimorene has lain down on the job, but don’t be fooled! She’s hard at work, creating a math investigation for your students to explore.

            Cats know how important it can be for students to experiment with math and try new things. Playing with ideas is how kittens (and humans!) learn.

            Cimorene wants you to know that the Make 100 Math Rebels Kickstarter offers a great way for human children to learn math through play. She encourages you to go watch the video and read all about the project.

            Too often, school math can seem stiff and rigid. To children, it can feel like “Do what I say, whether it makes sense or not.” But cats know that kids are like kittens — they can make sense of ideas just fine if we give them time to play around.

            So Cimorene says you should download the free sample journaling pages from the Math Rebels Kickstarter page. The beautiful parchment design makes doing math an adventure.


            [The free download will always be there, even after the Kickstarter project ends.]
            Make 100 Math Rebels Kickstarter

            Cimorene’s Puzzle Challenge

            Cimorene’s math puzzle is a classic geometry problem from the ancient Kingdom of Cats: Squaring the Circle.

            Draw a circle on your journal page. Can you draw a square (or rectangle) that has the same area?

            How would you even begin such a task?

            Notice Cimorene’s hint in the photo above: Try drawing the square that just touches the edges of your circle. (We call those just-touching lines “tangents” to the circle.)

            • What do you notice? Do the square and the circle have the same area? How close are they?

            The tangent square sets an upper limit on the area of the circle. You can see that any square that exactly matches the circle would have to be smaller than the tangent square.

            • Can you find a square that sets a lower limit on the area of the circle? That is, a square that must have less area than the circle?
            • What’s the biggest square you can draw inside your circle? Can you find a square that has all four corners on the circle?

            We call that biggest-inside square “inscribed” in the circle. Any polygon whose corners all sit on the circle is an inscribed polygon.

            • Play around with circles and squares. How close can you get to matching their size?

            Further Exploration

            After you have explored for awhile on your own, Cimorene has one more twist in her puzzle.

            In the ancient Kingdom of Cats, the wise ones estimated the area of a circle this way:

            Divide the width of the circle in thirds, and then in thirds again. (That is, cut the diameter into nine parts.) Draw a square with sides measured by eight such parts.

            You can try this on your journaling page by drawing a circle that is nine squares wide. Then draw a square overlapping it, with sides that are eight squares in length.

            • How closely do the areas match?

            Playing with Pi

            Here’s a surprise: Cimorene’s puzzle isn’t really about squares, but about calculus.

            The problem of Squaring the Circle is really a much bigger question: Finding the area of a square, rectangle, or other polygon is relatively easy, but how can we discover the area of a curved shape?

            For a circle, the area is related to the number pi, which is the number of times you would have to walk across the circle to equal the distance of one time walking around it.

            graphic by John Reid (cc by-sa 3.0)

            graphic by John Reid (cc by-sa 3.0)
            So the problem of Squaring the Circle is really the same as asking, “What is the value of pi?”

            • Can you figure out what approximate value for pi matches the 8/9 square used in the ancient Kingdom of Cats?

            If you’d like to learn more about pi, get ready for a celebration: Pi Day is coming soon! Every year, millions of children celebrate math on March 14th, because if you write the date as 3/14, it’s the same as the first three digits of pi.

            Find out more about playing with pi in my Pi Day Round-Up post.

            You may also enjoy:

            Share Your Stories

            Cimorene would love to hear about your children’s experiences playing with math! Please share your story in the comments below.

             
            * * *

            This blog is reader-supported.

            If you’d like to help fund the blog on an on-going basis, then please head to my Patreon page.

            If you liked this post, and want to show your one-time appreciation, the place to do that is PayPal: paypal.me/DeniseGaskinsMath. If you go that route, please include your email address in the notes section, so I can say thank you.

            Which I am going to say right now. Thank you!

            “Math Puzzle from the Ancient Kingdom of Cats” copyright © 2021by Denise Gaskins. Image at the top of the post copyright © Denise Gaskins.