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Q&A #19033


"Carrying" in addition

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From: Ralph (for Teacher2Teacher Service)
Date: Nov 25, 2007 at 08:47:23
Subject: Re: "Carrying" in addition

Dear Priya,

Thank you for writing to T2T. It sounds like your daughter has very good 
number sense, so she might find ways to solve 28 + 17 that are different 
from the so-called "traditional algorithm" [that we sometimes forget is 
only traditional in Britain and North America :) ], and hopefully her 
teacher is flexible enough to allow her to solve the example in her own way:
So, for example, she might think of 28 + 17  as 20 + 10 , and 8 + 7,
20 + 10 is 30,  and 8 + 7 is 15,  she might be able to do
30 + 15 in her head, OR might break it down further into 30 + 10 + 5, or 
40 + 5 = 45.  All the "carrying" part of the traditional algorithm does 
is what your daughter "thinks" when she's doing "10 jumps".  
                       
                      1
                      2 8
                  +   1 7
                 ----------
                        5       (thinking 8 + 7 is 15, which is 10 +5
                                 so I'll put the "10" with the other
                                 "10s" I have to add)

                      1
                      2 8
                    + 1 7
                    --------
                      4 5    (thinking: adding the "10s", I have
                              1 ten + 2 tens + 1 ten, or 4 tens,
                              which I write as a 4 in the tens place)
Hope this helps,

 -Ralph, for the T2T service

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