Q&A #13529

Teachers' Lounge Discussion: Addition and Subtaction with numbers 1-20

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From: Leonard

To: Teacher2Teacher Public Discussion
Date: 2005101613:19:52
Subject: Re: Subtracting using fingers

Ken Ong,

 You may want to try this new technique with your son, its called
Subdition. Subdition eliminates the concept of “borrowing” or
“regrouping”.  Three rules govern this technique:

1.The traditional rule is when the minuend (or top number) is larger
than the subtrahend(or bottom number) ‘8’ kids usually can master this
with a little practice.          -5

2.The Five Rule is when the minuend is smaller than the
subtrahend‘0,1,2,3,4’, a borrowing or regrouping scenario,  and the
subtrahend is 5,‘32’ add the minuend to the subtrahend which, in this
case is 7, -15  
 subtract 1 from the number left of the current column of the minuend
and continue processing.    

3.The Ten Rule state, that when subtracting numbers, if the minuend is
smaller than the subtrahend, and the subtrahend is not five, subtract
the subtrahend from ten and add the difference to the minuend. Record
the sum and subtract one from the number to the left in the minuend. 
32    10   2       32
                -16   - 6  +4      -16
                        4   6       16
This copyrighted method has been tested and was quite successful with
second grader. This technique is truly different from anything
currently being used in the educational system today.

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