Ms ds (7) adds "backwards" -- does it matter?

[Kate in Arabia]

Ds (7) is in Singapore 2A, he's started addition with renaming. We went through the whole "add then carry the tens" routine.

Today he had two pages of problems, all of them involving hundreds. First page I sort of walked him through it; he hemmed and hawed, lots of sighs; took quite a while to do about twenty problems. When we got to the second page he asked if he could do it "the way I always do it -- it's easier!" So of course I said sure. "his way" involves adding from the hundreds side down to the ones. He does it all in his head, and comes up with the answer very quickly. I almost couldn't believe it was the same child; he finished another 20 or so questions in a few minutes.

I will add that he is my innately "mathmatical" child; likes to spend his spare time making up math problems that he does in his head, then writes them out to show us (like 10,000 + 8,000 + 5,000 + 9). He is very much someone who likes to do things his own way, not necessarily the way that is "right" or "expected".

So my inclination is to just let him do these problems whatever way he wants, as long as he's getting the right answer and he isn't dragging. But I'm concerned it may cause an issue further on. Should I push him to do it the traditional way or leave him alone?

Thanks for your thoughts.

[LBC]

My dd is wanting to do the same thing, and I assume that it seems more natural to her because she reads from left to right, and therefore wants to add from left to right. I've been sitting with her and encouraging her to always add the ones first, because I know that in a couple of days we will be dealing with ones that add up to more than 9, and she will be frustrated about having to re-train her brain.

If you have a math oriented kid, maybe let him watch this little video clip about why borrowing works when he gets to the next level of adding/subtracting: http://www.youtube.com/watch?v=fWan_T0enj4&feature=channel It explains it in a very concrete way.

Lori

[Kate in Arabia]

He's already doing the renaming, he does it all in his head. Like 278 + 56. He'll add the hundreds, then the tens then the ones. The first couple of problems he did this way he kind of mumbled to himself, so I could hear he was adding then going back and adding more if something was carried before he moved on. Like "2 + 0 is 200; 7+5 is 12, so 320; 8 + 6 is 14, so 334." After the first two he did them all silently, and quickly. To me, I don't see how this is so much easier than the other way, but it isn't my brain, lol.

I don't know that it is necessarily tied to his reading, because he is also reading Arabic (not as fluently as English) which goes the other direction.

Edited to add:

My brother suggested giving him a really long problem, like 482,377 + 539,899, so he could see the difficulty in keeping all those numbers in his head. Maybe he won't find it difficult, lol. He makes up his own problems like that, I assume he's figuring them the same way.

[matroyshka]

Ds (7) is in Singapore 2A, he's started addition with renaming. We went through the whole "add then carry the tens" routine.

Well, when you get to 2B, there's a whole section on mental arithmetic, and they actually tell you for mental math it's easier to start with the tens (or hundreds) and add from left to right, and teach strategies to do it.

It sounds like your ds has already figured that out!

My not-so--math-minded dds had a breeze going through the column addition with renaming (sorry, I still call it carrying and borrowing), but then had a tough time doing it the mental math way.

It's not that one way is "right" and one way is "wrong" - they're just different strategies. Most kids like mine need to learn the column thing because they can only manage the right-to-left mental thing with fairly small or easier to add numbers.

[Asma_08]

My son did the same thing but when given a problem such as your brother suggested, he couldn't remember all of the numbers. So I now just remind him to start from the ones, it just seems they are less likely to make a mistake doing it that way.



Edited to add:

My brother suggested giving him a really long problem, like 482,377 + 539,899, so he could see the difficulty in keeping all those numbers in his head. Maybe he won't find it difficult, lol. He makes up his own problems like that, I assume he's figuring them the same way.

[nmoira]

My brother suggested giving him a really long problem, like 482,377 + 539,899, so he could see the difficulty in keeping all those numbers in his head. Maybe he won't find it difficult, lol. He makes up his own problems like that, I assume he's figuring them the same way.This is what I was going to suggest, not to change the way he does it mentally, but rather to illustrate the sense of the algorithm to use when it has to be done on paper. Maybe have a column of three or four numbers so it's more difficult to do mentally. FWIW, I have DD do as much math mentally as she's able.

[Kate in Arabia]

Thanks for your comments. I think giving him some larger problems (longer numbers, or more numbers in a column) are the way to go, I'm thinking about introducing it as a kind of game/challenge on the weekend..

thanks again..

[KarenNC]

I would watch to see if he has any problem doing subtraction related to this, and otherwise not worry too much. I know my daughter (who, though, is *not* mathematically inclined:)) made mistakes frequently for a while at that stage because she wanted to subtract in the wrong order (bottom to top) if it looked easier to her than borrowing. She had gotten used to doing the addition in either order ( ie 530 +26, it doesn't matter if you think of it as 0+6 or 6+0), but didn't easily make the switch to the fact that it *doesn't* work in subtraction (ie in 530-26 you can't start with "6-0 is 6", it has to be borrowing).

[Kate in Arabia]

I watched him more closely today, he had a page of three digit, three number problems (for example, 568+212+189). He was all over the place in how he tackled these, lol. A couple he did the traditional way (adding ones then tens then hundreds), several he added in his head the first two numbers, then added the answer and the third number, and the rest he did his "usual" way of hundreds then tens then ones. I can feel he is sort of conflicted how he wants to tackle the longer problems. There was almost an audible sigh of relief when he got a couple 2-digit numbers that he comfortably did his own way mentally.

I'm finding it fascinating to see how his mind is wrapping itself around these new challenges. My older ds is such a form follower, he never showed much interest in testing all these different techniques.

[Lori in MS]

My son does this too. I just left him alone and let him do it his way. This is what I recommend. I taught him the traditional way so he knew it. If for some reason it was too hard for him to figure out the other way he did it on paper the traditional way. It wasn't a problem. When I add mentally I always start with the hundreds. It's much easier mentally to do it that way. My dad was a whiz at mental math and he always did it that way too.

[Penny]

I taught my children to add and subtract from left to right. It is MUCH easier to do mental math that way. In fact, for larger numbers it is virtually impossible to do it mentally from right to left. It also encourages getting realistic numbers for the answer (ie estimating).

Subtracting is no problem. You must just borrow from the higher number after you subtract it. Also, we multiply the same way, and this very much encourages estimation of a realistic number. Long division is performed by everyone from left to right.

My kids are in 5th and have NO problems understanding the base 10 system and what they are doing.


Blessings,

Penny

[LizzyBee]

I've always added left to right, and sometimes I subtract that way too. I just glance over to the right to see how many I'll have to carry or borrow. I got A's in h.s. and college math, so I don't see any reason to force him to do it right to left.