> On 2015-11-29 04:48 AM (-4), Kenneth wrote:
>> This particular example-- multiplying two negative numbers and getting a
>> positive answer-- has always given me pause, philosophically. That
>> might sound
>> strange, coming from someone who considers himself (reasonably)
>> math-literate;
>> but I have always had a kind of built-in stumbling-block regarding it's
>> 'philosophical basis', and why or how this 'convention' came about, in
>> the
>> history of mathematics. ('Convention' may not be the correct way of
>> putting it,
>> of course; there have no doubt been many great mathematicians who have
>> struggled
>> with this concept in order to put it on a firm logical foundation. I
>> hope!)
>>
>> Put more simply: It seems perfectly 'obvious' that +3 X +2 = +6 (as
>> any child
>> discovers, when making two sets of three toy blocks, for example.)
>> Likewise, -2
>> X +3 should 'obviously' produce -6 ... although I can't think of a good
>> 'child's' example to illustrate that ;-) But when it comes to -2 X -3,
>> it just
>> doesn't seem 'intuitive' that it should produce a positive value.
>> (Although,
>> what *else* it should produce is certainly a mystery!) HOWEVER... I'm
>> not about
>> to question centuries (millennia??) of mathematical thought-- I'll
>> just accept
>> it. ;-)
>
> -2 x  3 = -6
> -2 x  2 = -4
> -2 x  1 = -2
> -2 x  0 =  0
> -2 x -1 =  2
> -2 x -2 =  4
> -2 x -3 =  6
>
> Seems intuitive enough.  I figured this out on my own as a kid, although
> I was suspicious of my own reasoning until it was confirmed in math class.
>

I had that same reasoning around 3rd or 4th grade. For the additions, it 
was in second grade.

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