Monday, November 05, 2007

math trick and the return of the internet

Just when I was about to cave in and pay for internet, the mysterious unsecured network reappeared. Yay! Assuming that it sticks around, I'm going to do my best to get far more prolific on your asses, so stay tuned!

In the mean time, let's do a fun math trick, shall we? First, grab a calculator, or pull up the one on your computer. Now punch in the first three digits of your phone number (not the area code). Complete the following operations, making sure to hit "enter" or the equal sign after each one:

multiply the first three digits of your number by 80
add 1 to the answer
multiply the answer by 250
add the last four digits of your phone number to the answer
add the last four digits of your phone number to the answer again
subtract 250 from the answer
divide the answer by 2

Recognize the number you got? Pretty cool, huh? I did this with one of my students, and she told me it was "hecka tight." Anyway, here's why it works:

Let x=the first 3 digits and y=the last four. Based on the instructions, we get:

[(80x+1)*250 + y + y -250]/2

Does everyone remember how to simplify an expression? We have to distribute the 250 into the 80x + 1, giving us 250*80x + 250*1 = 20,000x + 250. We also know that y + y = 2y, so we end up with:

(20,000x + 250 + 2y - 250)/2

The 250s cancel out, and then we divide by two, giving us:

10,000x + y

If you multiply, say, 123 by 10,000 you get 1230000. Obviously, if you add 4567 to that, you get 1234567.

Yeah, I know. That's five minutes of your life that you'll never get back. Sorry.

But look, here's baby M (practically toddler M now!), all adorable when I went up to Portland to visit:


4 comments:

Rebel said...

She could not be cuter if she tried!!!

I didn't do your math thing... if it doesn't spell 8008135 when I turn it upside down, I don't want to hear about it! ;)

T is said...

Math is FUN!!!

Rebel said...

Jenn - you have to check out M5K's blog today, it totally cracked me up.

http://michael5000.blogspot.com/

Plus, tomorrow he'll post the Thursday quiz that will make use of your extensive education & let you feel smug & self satisfied. ;)

marissa said...

ok i did it, and was amazed, but skipped over the part about how it was done--not on purpose--to look at the cute baby :)

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