From: Cooper <vrcooper@aol.com>
To: Teacher2Teacher Service
Date: Dec 11, 2001 at 20:26:52
Subject: Curious about fractions

What is the theory called when you are adding simple fractions, i.e. 3/4 + 
2/5 = and you just multiply the denominators (4x5 =20) and for the numerator 
answer, you just cross multiply and add (3x5 + 2x4), getting 15+8=23? The 
answer will be 23/20, which at that point you reduce.  Why does this work?  I 
saw someone doing it. It worked quite well, really quick, and I want to 
explain it to students.

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