Jump to content


adding left to right?

Recommended Posts

(I'm sorry, I'm SURE this is here somewhere, but I searched and couldn't find it.)


My "math kid" adds left - to - right (7yo). He's rarely wrong, and when he is, he self-corrects pretty easily, but it seems so much harder to me than going right to left.


Should I try to retrain him (in other words, is this going to come back to bite me later)? Or just let him go?


He's adding 3 3-digit numbers, and is okay with it - but I'm guessing it would be much harder if they were 5-digit numbers (but maybe not?).

Link to comment
Share on other sites

I was a middle school math teacher (before children) and I see nothing wrong with adding left to right, as long as he is getting the answer correct. In fact, in a real-life application, it would be more important to have the leading digits correct and be close to the correct answer, than to have the ones digits correct and be off by factors of ten.


But, how does he account for it when a the addends of a certain place exceed ten? Does he easily go back (or maybe I mean forward!?!) and adjust his sum?


In general, with a "mathy" kid, as long as he can explain what he is doing, I would not force with the "right" (ie - the way the book teaches) way as long as the answers are correct and he can justify his method to you.

Link to comment
Share on other sites

Yes, he "carries forward" in his head, and easily goes back. When he makes an error, though, this is where it is.


I had a solid math education, but it was very algorithm-focused vs. conceptually-based; in other words, I only know 1 or 2 ways to do something, and I don't intrinsically "know" the math.


This kid likes to order his problems sequentially based on their answers (i.e., he does all the sums, then re-numbers the page, just for the fun of it, highlighting the highest and lowest values).


This is an example of how he thinks:


309 + 471 + 218 = 900 at the beginning, then 80, then - oh, 18, so give 10 to 80 and arrive at 998.


(He hasn't done 4 or 5 digit numbers yet - my girls are older than he is, and I'm not sure they actually do the larger numbers mentally? Honestly, mental math AT ALL has been a new concept to me (Singapore), but I've noticed that I can now add wicked fast and my accuracy is greatly improved! hahaha!)


Thanks for the thoughts - I just don't want to let something go that is going to be harder to correct later on. I did show him my way, but he is not interested.

Link to comment
Share on other sites

Rightstart begins with adding left to right and then introduces right to left addition.


Think of some problems like 2006+32. For this problem it is much easier to add left to right. However when you have a lot of trades to make (eg. 10 tens for 1 hundred) then it is easier to add right to left. I would do 2845+569 from left to right.

Link to comment
Share on other sites

Our schools now teach a method where you write the sum on one line then draw connections between the numbers you are working with and add left to right. I always have to put zeroes in front when one of the numbers has fewer audits and to be honest I don't see the point. If I can do it that way I can probably do it mentally.

Link to comment
Share on other sites

When I saw my kids doing it, I always said something like, "That's great, you got it. But remember, eventually with math, going that way will be harder. We want to start with the units and move up to the tens, hundreds and thousands. It's just a habit you'll want to get into." And eventually they did start to hit problems where it was harder for them - especially with subtraction. And now they've mostly stopped doing it that way.


I agree that there's nothing wrong with it and I'm glad they learned to do it the "wrong" way, I just didn't want them to be surprised later, you know?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...