Teacher2Teacher 
Q&A #1493 
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From: Loyd <Loydlin@aol.com> To: Teacher2Teacher Public Discussion Date: 2010100311:31:47 Subject: Re: Re: why My last was too wordy. So, why do we invert: I can't make the divide symbol, so I will just use div. 3 2  div  ( 3/4 is a numerator and 2/5 is a denominator) 4 5 The denominator is also called the divisor. Next multiply the numerator and divisor by the same thing. That is, the reciprocal of 2/5 or 5/2. 3 5 2 5 15 15  x  div  x  =  div 1 =  4 2 5 2 8 8 So, you see it easier just to say, invert the divisor and multiply because it is the same thing. 1 is the identity element for multiplication and division, so we can ignore that. As I said in the previous post, the divide symbol almost disappears by the time you get to algebra.
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