Divisibility Test for Thirteen

My department chair, Sherry Ettlich, sent us a link to this video which shows a quick (new?) method of determining if a number is divisible by 7. After I figured out how it worked, it occurred to me to try the same method for divisibility by 13.  Here is how determine if a number is divisible by 13.

How to Check if a Number is Divisible by 13

How to Check if a Number is Divisible by 13

And here is a rough idea of why it works.

How to Check if a Number is Divisible by 13 Why it Works

How to Check if a Number is Divisible by 13 Why it Works

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About jrh794

I am a sixty-five year old math instructor at Southern Oregon University. I taught at the College of the Siskiyous in Weed California for twenty-six years. Prior to that I worked as a computer programmer, carpenter and in various other jobs. I graduated from Rice University in 1967 and have a MS in Operations Research from Stanford. In the past I have hand-built a stone house and taken long solo bicycle tours. Now I ride my mountain bike and play golf for recreation.
This entry was posted in Cool Ideas, Math Explorations and tagged , , . Bookmark the permalink.

One Response to Divisibility Test for Thirteen

  1. Nick says:

    I think the link to Sherry’s video is broken.

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