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Q&A #17351

Teachers' Lounge Discussion: alternative ways to mulitply

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From: julius nadas <jnadas@ccc.edu>
To: Teacher2Teacher Public Discussion
Date: 2007112423:30:43
Subject: bow tie multiplication

I believe that the bow-tie method was used back in Abraham Lincoln's
day and is just a graphic way of showing the FOIL method for
multiplying any pair of two digit numbers.  I hope this comes out OK
in your browser:

take 23 times 45.
In foil you add these terms:
20x40 + 20x5 + 3x40 + 3x5

in bow-tie you draw this picture:


20  +  3
 |\   /|      
 | \ / |     
 |  X  |     
 | / \ |      
 |/   \|
40  +  5

(see the bow tie) 
and you multiply the numbers that are connected by lines.



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