## Math Topics - Double digit addition and subtraction

kellybell
Posts: 473
Joined: Mon Jun 28, 2004 2:40 pm

### Math Topics - Double digit addition and subtraction

Renai wrote:I'm at a loss of how else to present this concept. Funny thing is, she gets the subtraction with borrowing. It's the addition with carrying that's causing her problems. I know she "gets" the subtraction because Friday she wanted to play a computer game that required both. I quickly showed her how to work the problems and every time I checked, her work was correct on the whiteboard.

I had initially skipped these chapters to firm up her math facts, and am coming back to them.

We've used base 10 blocks (even though she doesn't really like to use manipulatives) with a place value chart. She works stuff on the whiteboard. She still likes to split the numbers into units and tens. She'll add the right side, put that answer in a circle in the side, then put those numbers in the right columns. This afternoon she thought she'd get done quicker by adding the left side first. Of course, she had to erase all the answers. How frustrating is that!?

So I don't know what else to do. Any ideas? skip again until the end of the year? I'm up for it, lol! There's still plenty else to do in this book.
I know you said she doesn't like manipulatives, but pennies and dimes might work. Trade 10 pennies for a dime, etc. So, if you add 7 pennies and 8 more pennies, you make a group of 10 and trade it for a dime and have five pennies left over.

Since she already naturally understands borrowing, show her that she can borrow by trading the dime for 10 pennies. Maybe since she already gets this concept, when you add with the coins, maybe it will click in that direction too.

Play with those pennies and dimes!

I'd start with facts that she just might know (or easily figure out). For example, she probably knows that 9 + 2 = 11. You could easily model this with pennies. Make a group of 10, trade for a dime, and have one left over. After she's fine with demonstrating facts she knows, try problems she's not memorized (say, 32+88). Same concepts.

Another thing that I was reminded of when you mentioned adding the left first is that we had some silly motivational speaker at work (long before my mommy days) who asked us (a group of several dozen adults) how to add and everyone agreed "right to left." He showed us that you can just as easily add "left to right;" it's just not what we were taught. I had forgotten about it and don't really remember the concept (the speaker wasn't teaching math, just showing us to think out of the box or something -- I guess he didn't make much of an impact if all I remember is the math thing).

Anyway, if you add these numbers "left to right":

8 9
+ 3 5

You could add the 8 and 3 and put the 11 in the "tens column." Then when you add the 9 and 5, you put the 4 in the "ones column" and add the extra 1 to the tens column and you get 124. Same as if you went right to left. However, that's not how any curriculum that I know of teaches addition. I just remember this speaker saying it's just as easy. You're carrying all the same, but in a different way.

It's just figuring out what makes a kid understand, what makes that light go on. My youngest dd does fine in math ... once she gets a concept. Some concepts are like second nature to her and others are totally alien.
Kelly, wife to Jim since 1988, mom to Jamie (a girl, 1994), Mary (1996), Brian (1998) and Stephanie (2001).
cbollin
kellybell wrote: However, that's not how any curriculum that I know of teaches addition. I just remember this speaker saying it's just as easy. You're carrying all the same, but in a different way.

It's just figuring out what makes a kid understand, what makes that light go on.

Singapore math teaches something similar to this, doesn't it? Or maybe the dust from cleaning my basement is got to my head and I just think that Singapore introduces this in the end of 1B? Except that Singapore doesn't teach it this way vertically, it does it horizontally. When Singapore gets around to the vertical stacking, it does more traditional carrying style.

-crystal
Renai
Posts: 35
Joined: Fri Dec 02, 2005 12:48 pm
Location: New Mexico
Contact:
I'd forgotten about money, silly me. She likes money :). I'll try that today. Does it seem strange that she can borrow, but forgets regrouping?? Or is it just me?

It's funny you mention adding from left to right. I actually do that now that I'm older. Don't know when I figured it out, but it's not something I was taught. The only reason I wanted dd to do right-left is because I thought it would help her to see for example with 15, put 5 in the ones total and the 1 in the tens column. She kept forgetting to carry the one. Hmmm, you know, yesterday she did start writing the number correctly- from left-right. I'll see how it goes today.

(I'm actually using Singapore as a supplement, but we only have 1A so far.)
Renai
Wife to Enrique
Mom of two dd- 9/99 & 1/11

Bilingual homeschool
2004-05 SL
2005-2012 MFW
2012-2013 K12
2013-2014 dual-language charter
2014-2015 MFW Ancients/young'un- MFW preschool, reading books

http://creativeplaybilingual.blogspot.com/
donutmom
Posts: 67
Joined: Tue Nov 21, 2006 5:41 am
Pennies and dimes are what clicked for our son.

My nephew got the borrowing right away, too, but not the carrying. So you're not alone!

Another idea. . . use graph paper with larger squares (large enough for your child to manage to write a number in each square). Then have the problems on the paper--whether you or she write it. Tell her you can only have one number in each square. So when they add the 7 + 5 in the ones column, they can't write 12 in the square below it. So show how to write the 2 and carry the one. Can work well with the money on hand as well.

Did I write that in a way that makes sense?? Maybe not. I'm coming off a not so nice case of the flu, and hubby's out of town, besides the house being in a state of remodeling. I don't really know if I'm coming or going right now! I guess I'll be going now--to bed.

Dee
Renai
Posts: 35
Joined: Fri Dec 02, 2005 12:48 pm
Location: New Mexico
Contact:
Yes, Dee, that makes a lot of sense! I'm glad we're not alone in the borrowing/carrying thing too. I actually do have that graph paper in the house (somewhere- been put away for a couple of years now).

We took a break from math yesterday... we'll be back at it today with money and graph paper.

Thanks all for the assistance!
Renai
Wife to Enrique
Mom of two dd- 9/99 & 1/11

Bilingual homeschool
2004-05 SL
2005-2012 MFW
2012-2013 K12
2013-2014 dual-language charter
2014-2015 MFW Ancients/young'un- MFW preschool, reading books

http://creativeplaybilingual.blogspot.com/