Tag Archives: puzzle

What is Multiplication – part X

Posted on 2009/04/29 by Bert Speelpenning

Yesterday, in the supermarket, a customer dumped a whole basket full of power bars on the counter.  The checkout counter person started to scan them in, one by one.  After seeing about seven of them scanned, with a lot more … Continue reading →

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Math in the Comics – part 10

Posted on 2009/04/26 by Bert Speelpenning

From last week’s Foxtrot comic, another take at the cultural background conversation of math. Who is bad at math? At one level, a puzzle.  The top part, the part that starts with “16-11-13-5” is not a subtraction problem.  It is … Continue reading →

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A Collatz-Inspired Puzzle

Posted on 2009/02/27 by Bert Speelpenning

This is a puzzle. In prior posts, I used the Collatz Problem, restated here: Each counting number n past 1 is assigned a successor number, as follows: The number “1″ is considered home, and when you’re home, you stop.  If … Continue reading →

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Mathematical Puzzle – Hinges

Posted on 2009/02/20 by Bert Speelpenning

This is a puzzle. Imagine I have three rods of length 1 each, and they are connected together with perfect hinges.  Together, they form a somewhat flexible shape ABCD (with AB=1, BC=1 and CD=1), even if I fix the two … Continue reading →

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Math in the Comics – part 2

Posted on 2009/02/08 by Bert Speelpenning

Today, Bill Amend has another comic strip with math in it: It plays on the Fibonacci series, which these two geeks obviously know well.  The starting numbers of the Fibonacci series are 1, 1, 2, 3, 5, 8, … and … Continue reading →

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Notes on Divisibility – Common Divisors

Posted on 2009/02/02 by Bert Speelpenning

In an earlier post I introduced the notion of a divisor without relying on division, instead thinking of it as a mark that was left during skip counting. This is a very old notion, dating at least to the times … Continue reading →

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Powerful Sunglasses

Posted on 2009/01/28 by Bert Speelpenning

This is a puzzle. Imagine I own a pair of sunglasses that reliably blocks ultraviolet rays so that, out of any ten rays that shine on it, only one of them gets through.  So, if 40 rays shine on them, … Continue reading →

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Half a pizza and half a balloon

Posted on 2009/01/26 by Bert Speelpenning

This is a puzzle If you’ve ever actually tried to divide a pizza into 15 equal pieces – and I mean the kind of dividing that uses a knife or a cutter or piano wire – you’ll find that knowing … Continue reading →

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Making Change – A Sam Lloyd puzzle

Posted on 2009/01/25 by Bert Speelpenning

This is a puzzle, taken from the famous puzzle producer Sam Lloyd, complete with original illustration.  This puzzle is old: A lady bought a boquet at the florists for thirty-four cents and had a one dollar bill, a three cent … Continue reading →

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The Lewis Carroll problem

Posted on 2009/01/24 by Bert Speelpenning

This is a puzzle. Lewis Carroll, the author of Alice in Wonderland, was also a mathematician. In his diary for 1890, he wrote the following statement: is always the sum of two squares where x and y are a pair … Continue reading →

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