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Adding Left to Right


Date: 4/5/96 at 1:50:19
From: Sean Frances Aurora Devin
Subject: MathMagic

Hi- I am a parent of 5 children, 3 of whom are school-age. Because 
of my own math illiteracy, I have been reading out of a book 
titled _Math Magic_ by Scott Flansburg, "The Human Calculator". He 
teaches to add from left to right - the same direction we read - 
rather than the right to left method my children have been 
learning in school.  I am having problems with some of his 
problems. Here are 2 problems that have me stumped:  

8,703
2,961                                                                      
+
343       

and the other one:

9,272
5,498
27
2,309
8,565                    

In the first problem, I can't figure out what
happens to the 9 left over from the 19 total after I carry the 
10 to the thousands column. (Remember - we're doing this from left 
to right - try it.)

In the second problem, I'm just totally confused. Will you please 
try these in this unique way and tell me how you do?  The way I 
was taught in school where I add from right to left and carry is a 
breeze of course. Also, tell me if any of you math whizzes use 
this method, or are you familiar with it?

What is your personal opinion?       Thanks - MOM


Date: 4/29/96 at 21:36:41
From: Doctor Jodi
Subject: Re: MathMagic

Hi there! 

This is an intriguing idea.  I'd forgotten how difficult 
"borrowing" and "carrying" could be.   

I have, upon occasion, added left to right in my head, but never 
before on paper, so this was an interesting experience for me.

I think that adding in "columns" might make this easier for you.
(It did for me!)

Here's what I mean:

I add the first column and write 24, then the second, and third, 
and last.

 9272
 5498
   27
 2309
 8565
------
24
 14
  24
   31

Do you see what I've done?

Now I add the numbers that correspond to the same place value:

24
 14
  24
   31
-----
25671

Does this make sense?

Try this for the first problem and see if it helps... You'll find 
that you'll have to "carry" once again, but I think it might be 
simpler if you can see what's going on.

Good luck and let us know if you need more help... What do your 
kids think of this method?

I think that it's really important to remember that there's no 
single "right" way to do math, so ideas like left-right addition 
are VERY important...

-Doctor Jodi,  The Math Forum

    
Associated Topics:
Elementary Addition

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