Mrs. Boyer’s 7th Grade Weblog

At the beginning of the week, I read this assignment and worried that I would have nothing to write about. How embarrassing would that be that a math teacher didn’t encounter any math throughout the week? Now that it is time to do the assignment, I find myself choosing from several events.

A teacher at my school sent out an email with the subject, “How does this work?” It was a link to this page: http://www.milaadesign.com/wizardy.html. She seemed to think that it really might be magic, and that her computer really could read her mind! I took a quick look and figured there was math behind it, and later that day, when I had time, returned to the site for a closer examination. The site asks you to pick on 2-digit number. Then you add together the digits and subtract the sum from your original number to get your answer. Then it shows you an assortment of pictures paired with numbers. You are supposed to stare at the image that matches with your answer for 10 seconds. While staring, your image shows up and enlarges in the center of the screen; just as if the computer might be reading your mind! You might want to check out the site to see for yourself.

That afternoon I emailed her back with the following explanation. It turns out that you can let xy represent the 2-digit number. The tens-digit is represented by x, and the ones-digit by y. This value of this number would be 10x + y. Then you subtract from that (x + y), giving you (10x + y) – (x + y) which simplifies to 9x. Thus, your “answer” from above will always be a multiple of 9. All multiples of 9 such as 9, 18, 27, 36, 45, etc. are paired with the same symbol, so no matter what multiple of 9 you are looking at, it will be the same image that appears on your screen! Then, so you don’t get suspicious when you try it again, they mix up the symbols so you won’t get the same symbol each time! I don’t know who has enough time on their hands to design a website like that, but I thought it was pretty cool. The next chance I have to use my mobile lab with my students, I am going to have them try the website for sure!