Ostomachion: Divide the Square

archimedes, studying

“Puzzles are made of the things that the mathematician, no less than the child, plays with, and dreams and wonders about, for they are made of things and circumstances of the world he [or she] lives in.”

—Edward Kasner

Long ages ago, one of the greatest mathematicians of all time played with a children’s puzzle.

The puzzle was called “The Ivory Challenge”—or something like that, translations vary. Ostomachion in Greek. Fourteen ivory polygons (flat shapes with straight sides) were supposed to fit into a square box.

Archimedes solved that puzzle. But like any good mathematician, he didn’t stop there. The solution to any puzzle is only the beginning, a doorway to further adventures.

So Archimedes asked himself one of the big questions of mathematics: “How many ways?”

The Ostomachion is a rather complex puzzle, and our students may struggle to figure out where to start. One of the classic tools in any mathematician’s toolbox is to make it simpler. So let’s begin our own investigation with a simpler challenge:

  • How many ways can you bisect a square?

Continue reading Ostomachion: Divide the Square

Reasoning about Ratios and Proportions

photo of sailboat on the Nile river

“The value of a problem is not so much coming up with the answer as in the ideas and attempted ideas it forces on the would-be solver.”

—I. N. Herstein

Whenever I give a problem or puzzle in an Alexandria Jones story, I’ll try to post the answer soon afterward.

But don’t peek!

In the old days of my snail mail newsletters, the answers always came in the next issue, so students had two months to let the puzzle ruminate without temptation.

After all, if you only read the answer I give, you miss out on the fun of solving the puzzle. Follow the Math Adventurer’s Rule:

  • Figure it out for yourself!

Give the problem a good workout on your own. See what you can notice about the puzzle. Wonder about how it connects to the larger world of mathematics.

Play with the ideas and find out where they may lead.

Then check the answer just to prove you got it right, and maybe to see whether we did it the same way. There’s always more than one way to approach any math problem, and each method offers its own insights.

Continue reading Reasoning about Ratios and Proportions

The Secret of the Pharaoh’s Treasure

caravan in Egyptian desert

“I am inclined to believe that one of the origins of mathematics is man’s playful nature, and for this reason mathematics is not only a Science, but to at least the same extent also an Art.”

—Rózsa Péter

This week, we have the first mathematical adventure of Alexandria Jones, which takes place in the early days of her father’s archaeological expedition mentioned in the introduction post.

Herein we meet the one major character who is not named after a mathematician from history: Alex’s nemesis, Simon Skulk.

While my fiction doesn’t rise close to the level of “art,” I hope it offers a glimpse into the playful nature of mathematics for you and your children.

Continue reading The Secret of the Pharaoh’s Treasure

Introduction to the Science of Counting

fantasy elf archer

One of my favorite rabbit-trails to explore in middle school math is the science of counting and probability.

It’s a great topic because the calculations are relatively easy, mostly multiplication and division. But there’s a lot of thinking that goes into figuring out just what calculations we need to do.

Counting is not only for little kids! It’s part of discrete mathematics, which means the study of things that are not continuous—things that come in discrete chunks—and it’s important in game design, computer programing, and cryptography.

Prealgebra and Geometry games book

This post is a section of my Prealgebra & Geometry Games book where my daughter and I explore the fundamental counting principle, the key to solving many counting and probability puzzles.

Continue reading Introduction to the Science of Counting

Probability Puzzles with Obsolete Coins

jar of coins

I love math puzzles, and Henry Ernest Dudeney is the foremost puzzlemeister of all time.

Whenever I need a diversion from the pressing day-to-day busyness of life, I like to crack open one of his books. And get humbled. He stumps me as often as not, but I enjoy the challenge.

Today, I’ve got two of his somewhat-easier puzzles from Amusements in Mathematics, dealing with the probability of obsolete coins tossed or pulled from a bag.

Okay, so the penny isn’t obsolete quite yet, even though the US government quit making them. But the “penny” in these puzzles is the old British pence, which went out of date seemingly ages ago, along with all the other non-decimal coins that made old math puzzles so confusing.

Probability puzzles are great for middle school students because the arithmetic itself is simple. The challenge is in figuring out exactly what calculation to do.

Have fun playing math with your kids!

Continue reading Probability Puzzles with Obsolete Coins

Conversion Factors: How Old Are You in Nanoseconds?

birthday cupcake with sparkler

Homeschool Memories

[Based on a problem I made up for my co-op students, once upon a time…]

Conversion factors are special fractions that contain problem-solving information. Why are they called conversion factors?

  • “Conversion” means change, and conversion factors help you change the numbers and units in your problem.
  • “Factors” are things you multiply with. So to use a conversion factor, you will multiply it by something.

Continue reading Conversion Factors: How Old Are You in Nanoseconds?

This Puzzle Is Murder

cartoon detective

Do you sometimes mourn (in a small way) the loss of a favorite website? I still miss the Daily Set puzzle, which was part of my morning routine for years.

But lately, I’ve added a new teaser to wake up my brain for the day.

While Set was a visual-logic puzzle, this one is straightforward (though not simple) deduction. I think you’ll enjoy it.

Continue reading This Puzzle Is Murder

Tasty Treats from the Moscow Puzzles

basket of apples

“Problems stressing deduction rather than calculation have a special appeal and value. They teach you to analyze, and to seek unorthodox ways of solving a problem.”

—Boris Kordemsky

Today I’m sharing a few treats from The Moscow Puzzles by Boris Kordemsky, which mixes classic brainteasers and original stumpers.

Recreational math expert Martin Gardner called Kordemsky’s book “the outstanding puzzle collection in the history of Russian mathematics.”

Have fun playing logic with your kids!

Continue reading Tasty Treats from the Moscow Puzzles

Rescuing Cool Math for Older Kids

mother and teen daughter do homework together

Do you have math dreams for your children?

Here are some dreams shared the authors of Avoid Hard Work!

For our children, we dream that mathematics…

  • … makes sense.
  • … is more than just arithmetic.
  • … is joyous.
  • … makes them strong.
  • … is meaningful.
  • … is creative.
  • … is full of fascinating questions.
  • … opens up many paths to solutions.
  • … is friendly.
  • … solves big problems and makes the world better.
  • … is a powerful tool they can master.
  • … is beautiful.
  • … lets them learn in their own ways.
  • … is connected to their lives.
  • … asks “why” and not just “how.”
  • … opens the world.

Continue reading Rescuing Cool Math for Older Kids

Puzzle: The Eccentric Teacher

boy and girl ready to solve math puzzles

One of my favorite things as a teacher was to gather a group of children to play math together.

Call it a math club or math circle, the name didn’t matter, but the activity was always fun. We did non-schooly games and projects, and the kids enjoyed both the camaraderie and the experience of thinking hard in a stress-free setting.

If you’d like to pull together a math club/circle of your own, here are some tips.

Today’s puzzle involves an unusual teacher trying to collect students to participate in a group activity…

Continue reading Puzzle: The Eccentric Teacher