Subject: Re: Double negatives
Date: Wed, 15 Jul 1998 03:07:26 +0300
From: Bonnie Warmund Teboul

When I learned this rule I was convinced that I would prove my teacher wrong.

Some where in college I finally convinced myself that it really does make sense!!

Try a chart 3x10

0 = 300    -3x 100= -300
            3x 10 =  30    -3x  10=  -30  
            3x  1 =   3    -3x   1=   -3 
            3x  0 =   0    -3x   0=   0 
            3x -1 =  -3    -3x  -1=   ?
												3x-10 = -30    -3x -10=   ? 
             ...            ... 

Follow the progression and you can easily understand what is happening without mirrors.

As we multiply a positive number by progressively smaller numbers the answer gets progressively smaller. When we multiply a negative number by progressively smaller numbers the answer becomes progressively bigger! (because it is less negative)

If you want a practical example, try thinking of a bank account. Say you deposit $20 a month then

3 months in the future you have +3 x +$20 = +$60 (more than today)
3 months ago you had            -3 x +$20 = -$60 (less than today)

Now say you withdraw $20 a month then

3 month in the future you have  +3 x -$20 = -$60 (less than today)
3 months ago                    -3 x -$20 = +$60 (more than today)

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