Let’s Play Math!

[Rescued from my old blog.]

Once again, Rudbeckia Hirta brings us some funny-but-sad mathematics. The test question was:

Without factoring it, explain how the number
N = (1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 x 11) + 1
can be used to argue that there is a prime number larger than 11.

Take a few minutes to think about how you would answer that. Okay, if you haven’t seen a similar proof before, you are allowed to take as many minutes as you need! Euclid’s famous proof of a closely-related theorem (The Infinitude of Primes) is featured in one of my favorite math-for-the-layman books, Journey through Genius: The Great Theorems of Mathematics.

Then click over to Ms. Hirta’s blog (Learning Curves) to read the answer given by a college honors student. In the first comment post, oxeador explains the student’s reasoning.

And for those of you who haven’t heard the joke before, here is an extended list of reasons why all odd numbers are prime.

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Check out these related posts: more math humor