April 19, 2007

The Sun!

Posted by Scott at 09:43 PM

Weather - I stepped out for lunch today and was shocked as I crossed the parking lot! I had forgotten that the sky could be blue. And that bright orb in the sky, what is that!?

After what seemed like endless days of gray combined with rain or at least drizzle, the weather gave us a taste of what spring is supposed to be about. By mid-afternoon Milford hit 67°F. Thank you Lord!

Claire - For the first time in recent memory — at least years — Claire stayed home sick today. It broke her heart to do so. There was some concern over ruining her attendance record but also over getting behind in her studies. I tried to console her by saying that I didn't think one should get an award for perfect attendance. In my mind it's like giving Milford an award for not having any tornados this past year. I can't control that. While there are things we can do to reduce our odds of getting sick, sooner or later everyone does. Michelle found it odd that the school will give awards for attendance, but won't give performance awards until middle school because they don't want to play with children's self esteem.

Michelle - Meanwhile the infection on Michelle's finger doesn't seem to be getting any better. She's going back in tomorrow to see a doctor for another opinion. I hope they get to the bottom of this soon. If it were me, with my high reliance on typing, I'd have been a squeakier wheel about this.

AMD - If you follow the news, AMD recently made public that their first quarter results were $611 million dollars of net loss. (see more at the WS Journal coverage) It was less than a year ago that Intel was laying off thousands.

Advanced Micro Devices Inc.'s first-quarter loss was larger than Wall Street expected, but some market watchers expressed optimism that the most brutal phase of a price war with Intel Corp. may be ending.

While I don't think we'll ever see an end to our competition with Intel and nVidia, I can only hope that cutthroat prices wars cease soon.

Help - I'm in need of help in explaining a math concept to Claire. The example I'd like to explain is why 5 - (-3) = 8. In other words the concept of subtracting negative numbers as being equivalent to adding a positive. The example I was thinking of is the following.

Suppose Claire has $8 in her purse. We're at the mall and she forgot to bring her purse. Stopping by Claire's Accessories, she sees a trinket she'd like to buy for for $3. I offer to buy it for her and she can repay me later when we get home. One might say that her net spending money is now $5. When we get home, her report card comes in and she gets a good grade in a class she was having difficulty with. I offer congratulations and say, “just for that, I'll take away your debt of $3.” (And take you out for ice cream, of course!) Thus, she had a net spending amount of $5, I took away $3 of debt, and now she has a net spending amount of $8.

Can anyone think of a better example? Hey Bill White, does the Mathematica website have any gee whiz interactive demos? Math major David Brooks, any ideas? For me subtracting a negative is just something I've known how to do for so long I don't even think about it. But like me, Claire likes to visualize and intuit things about numbers. She'd like an example she could wrap her head around.

Comments

Hoo boy. I just tried to find a way to explain it and got corn-fused. Maybe that's why I have trouble with money :-) Way back when I think I just worked the rule so I could get the answer and move on. That's what happens in my head nowadays when I see that: I refer to the rule "minus a minus is a plus" or somesuch and do the addition. I'll ask the social mailing list at work for advice & demos.

Posted by: Bill White at April 19, 2007 10:11 PM

This is a good example of why negative numbers were not considered "real" for millennia (just like "imaginary numbers" - square roots of negative one - were considered unreal for a long time, as well).

Think of a negative number as a debt. If you add a negative number, you pay off the debt. So adding negative-three dollars to five dollars is the same as paying off a three-dollar debt, leaving you with two dollars. 5 + -3 = 2.

Subtracting a negative number is *incurring* the debt - borrowing the money in the first place. You have five dollars, you subtract negative-three dollars (that is, borrow three dollars) ... and now you have eight dollars. 5 - -3 = 8.

Or if you're an English major, think of double-negatives in sentences, because they operate the same. "I'm not unable to figure this out" means "I am able to figure this out" - the two negatives cancel each other other, so to speak. Just like subtracting a negative number.

Or just have a mental image of the subtraction sign spinning 90 degrees and overlapping the negative sign, turning them both into one plus sign, and forget the reasons why. That's how I learned it as a kid.

Posted by: Dave Brooks at April 20, 2007 08:28 AM

Hi Dave and Bill,

Thanks for the help.

It's funny that you mention the grammar aspect. I had thought of that. Of course, I also work in the digital/boolean domain, so that also makes it obvious to me.

Then there's the recent movie trailer for Shrek the Third. When they interrogate the wooden puppet, he's full of inverted and double negative speak.

http://www.youtube.com/watch?v=ogSymbTORnc

Posted by: Scott at April 20, 2007 08:41 AM

Ahah! We finally know what Michelle has. She has a case of Paronychia. See also:

http://en.wikipedia.org/wiki/Paronychia

http://www.aocd.org/skin/dermatologic_diseases/paronychia_nail_in.html

She's on her way to the local pharmacist to get an appropriate oral antibiotic.

Posted by: Scott at April 20, 2007 02:19 PM

Come back to River Grove. Life is simpler. 5 - (-3) = 2 at St. Cyp's, that's according to Peter's and Cassidy's Math teacher. That drove Alyssa crazy!!! But maybe that give Claire another 30 some years to get it. :-)

Posted by: Uncle Butch at April 22, 2007 06:37 PM

Really! Wow! Did Alyssa ever get it clarified?

I don't understand. The teacher's materials usually have answers on them. How did it get taught that way? Did the teacher think the materials were wrong?

Posted by: Scott at April 23, 2007 06:06 AM