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EMU math department blog » fun stuff File Not Found – Eastern Mennonite University
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A Christian university like no other - Eastern Mennonite University

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EMU math department blog

category: fun stuff

Oops! Error on the Problem Corner

March 17th, 2009 – by byer

In the Problem corner of our Winter 2008 Integram (http://www.emu.edu/math/integram/winter2008.html), we asked readers to find a collection of 21 distinct whole numbers where the sum of the reciprocals of those numbers was 21.  We received a number of correct solutions (thank you readers!).  We (okay, I) also felt compelled to include our own solution, because it cleverly used properties of Mersenne Primes and perfect numbers.  However, we (okay, I) were wrong!  Our (okay, my) proof used the “fact” that 2047 was prime.  However, as Dan Reinford (EMU, class of 1951) pointed out in private email correspondence, 2047 is the product of 23 and 89!  And so it is.  A perfectly beautiful proof just went poof.

You’ve got to admit, though, that 2047 certainly looks prime!  Anyway, thanks to Dan for pointing this out…certainly I feel a bit sheepish now, and I’ll make sure to be more careful with the solutions I provide to my own problems!

Owen

Posted in fun stuff, math | No Comments »

EMU the bird

December 13th, 2007 – by Yong Zhang

Wondering around in Washington zoo last summer, I suddenly saw the name “EMU”. “How does EMU have anything to do with Washington zoo?” I was suprised, “Is the biology department running a joint project with the zoo?”. Looking carefully, I realized that it was EMU the bird, the largest bird native to Australia.

EMU the bird

Out of curiosity, I googled the term “EMU” to find out who Google thinks deserves this name the most. Google uses a PageRank algorithm (a more detailed description here) to rank their search results. It is one of the core algorithms that make the Google search engine popular. To my delight, currently we are the number two link in Google research results, beating Eastern Michigan University, EMU the bird, and lots of others.

See you next semester.

Posted in CS, fun stuff | No Comments »

A planarity game

November 27th, 2007 – by Yong Zhang

Graph theory is one of the topics in discrete mathematics. It is also important for a CS major to know some graph theory since many real-life problems concerning computer networks and computer circuit design are in fact problems in graph theory.

A planar graph is a graph that can be drawn on a piece of paper without any edge crossing. It is especially important in areas of computer engineering such as VLSI design. Determining whether a given graph is planar is not hard, but finding the planar drawing of a planar graph can be quite time consuming — check out the planarity game. It took me about five minutes to finish the first three levels, then the game gets more challenging…

Posted in CS, fun stuff, math | No Comments »

Why do computer scientists always confuse Halloween and Christmas?

October 31st, 2007 – by Yong Zhang

Happy Halloween!

Computer scientists deal with various number systems. In addition to the Decimal (Base-10) number system, which everybody uses, computer scientists use number systems such as Binary (base-2), Octal (Base-8), and Hexadecimal (Base-16). Computer scientists even come up with many jokes about number systems.

There are 10 kinds of people in the world, those who know Binary and those who don’t.

Does this sentence make sense to you? Which category do you belong to? If you are a CS major and you fall into the second category, come to my office and get educated. This sentence also has a math version:

There are three kinds of people in the world, those who can count and those who can’t.

I certainly hope you fall into the first category.

Why do computer scientists always confuse Halloween and Christmas?

Because Oct 31 and Dec 25 look the same (value) to us. I will let you ponder on why I say so.

Posted in CS, fun stuff | No Comments »

File Not Found – Eastern Mennonite University
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