Re: [xmca] a minus times a plus

[Linda Williams <lwilli55@emich.edu>]

Hello folks.  You're inspiring this lurker to post.  Here's how I,  
another literacy person, learned it.

Good guy = + (positive)
Bad guy = - (negative)
Coming to town = +
Leaving town = -

Good guy comes to town (+*+) = +
Good guy leaves town (+*-) = -
Bad guy comes to town (-*+) = -
Bad guy leaves town (- * -)= +

Add a background scenario of the stereotype of the old West in  
America, and you have the whole picture.  I guess this is just a  
narrative around the "leave it alone/reflect it through a mirror"  
pattern Jerry Balzano spoke about.  I found a narrative like this  
really helped my 12 year old former students get this pattern. . .

Linda Williams

Linda Williams, Ph.D.
Assistant Professor
College of Education
Department of Teacher Education
Reading Program Area
313C Porter Hall
Eastern Michigan University
Ypsilanti, MI 48197
734-487-7120 , Ext. 2635
Fax:  734-487-2101

lwilli55@emich.edu



On Apr 27, 2009, at 11:53 PM, Duvall, Emily wrote:

> My non-math vision.
> If I multiply a positive number by 0, I still have 0.
> If I multiply a positive number by less than 0, a negative number, I
> will still have less than 0... only it will be a more specific  
> amount of
> less than zero.
> Ergo multiply a positive number by a negative number and it will  
> have to
> be a negative result.
> ~em
> P.S. I teaching reading.
>
>
> -----Original Message-----
> From: xmca-bounces@weber.ucsd.edu [mailto:xmca-bounces@weber.ucsd.edu]
> On Behalf Of Mike Cole
> Sent: Monday, April 27, 2009 3:48 PM
> To: eXtended Mind, Culture, Activity
> Subject: [xmca] a minus times a plus
>
> Since we have some mathematically literate folks on xmca, could  
> someone
> please post an explanation of why
>
> multiplying a negative number by a positive numbers yields a negative
> number? What I would really love is an explanation
> that is representable in a manner understandable to old college
> professors
> and young high school students alike.
>
> mike
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