Squawky Acres Posted December 31, 2015 Share Posted December 31, 2015 I was wondering if it is the new thing to teach multi-digit subtraction by beginning at the left with the highest place value, and then proceeding to the right. RightStart Math Level C teaches it this way, but Saxon 2 and Singapore 2 seem to teach it the traditional way, which makes more sense to me (eliminates the possibility of a student subtracting numbers with different place value, makes trading easier, etc.). Would I be doing RightStart all wrong if we subtracted ones first? I do like the rest of RS Level C, but have just run into this one problem. Quote Link to comment Share on other sites More sharing options...
Kiara.I Posted January 1, 2016 Share Posted January 1, 2016 This question comes up a lot on the RS mailing list. Does your child have trouble with it as-is? You could mention that some math programs teach it starting on the right, and others teach it starting on the left, and let your student select her own preference. If you're doing it on the abacus, there's not a lot of room for errors due to trading. They pull it down, see that the next needs a trade, pull another bead done, and carry on. 2 Quote Link to comment Share on other sites More sharing options...
athomeontheprairie Posted January 1, 2016 Share Posted January 1, 2016 I learned right-to-left. I use RS for my dc. They use left-to-right. I taught them the RS way. I love it. They love it. They (hardly) ever make a mistake with trading, or place value. I did show them my way. Occasionally they use that, but seldom. Agreeing with the pp: I would teach the RS way. I would teach the other way. Once they can do it both ways, I would then let me dc decide what they want to use. 1 Quote Link to comment Share on other sites More sharing options...
Squawky Acres Posted January 1, 2016 Author Share Posted January 1, 2016 Thank you for the suggestions. I'm not on the RS mailing list, but will see if I can figure out how to get on. They are used to the right-to-left way from Saxon, and had no trouble with it; so the RS way seems odd to them as well. I was just wondering if there is value in continuing to show them the RS way, or if we should just get on with other things. We are in an odd position, as we are re-doing 2nd grade math. My son did Saxon 2 in first grade, and is now doing RightStart's 2nd grade program, as I felt it covered some additional material that he needed, and I didn't want gaps in our transition. Quote Link to comment Share on other sites More sharing options...
Sarah0000 Posted January 1, 2016 Share Posted January 1, 2016 I've been showing DS both ways. Just depends on what makes sense for that situation, but I'd say I probably do left to right more frequently. Its my personal opinion based on zero years of experience (haha) that its best to teach and encourage multiple methods in order to discourage rote application, unless a kid is really struggling. 2 Quote Link to comment Share on other sites More sharing options...
Jackie Posted January 1, 2016 Share Posted January 1, 2016 I was wondering if it is the new thing to teach multi-digit subtraction by beginning at the left with the highest place value, and then proceeding to the right. RightStart Math Level C teaches it this way, but Saxon 2 and Singapore 2 seem to teach it the traditional way, which makes more sense to me (eliminates the possibility of a student subtracting numbers with different place value, makes trading easier, etc.). Would I be doing RightStart all wrong if we subtracted ones first? I do like the rest of RS Level C, but have just run into this one problem. RS has always taught it left-to-right, so it's not new. But they're the only program I'm aware of that does it this way. Neither way is inherently better, and if you want to teach it right-to-left while using RS it'll be just fine. I'd suggest you teach it to your children both ways - while most people do right-to-left on paper, many do left-to-right for mental math. 1 Quote Link to comment Share on other sites More sharing options...
eternallytired Posted January 1, 2016 Share Posted January 1, 2016 I was trying valiantly to do it the RS way, but my kids naturally were doing it the R-to-L way and were getting confused when I tried to re-orient them. After a couple days of confusion, I just said, "Here's how this book teaches subtraction. [Did a problem the RS way, explaining as I went.] Here's how you are doing problems like this. [Did the same problem R-to-L.] As you can see, both ways work--they both get you the same answer. You may pick which way makes more sense to you as you work through subtraction problems." They understood that there were multiple ways to do the same problem and felt empowered that I wasn't forcing to work in a way that didn't make sense to them. And yes, I have noticed that they naturally do R-to-L on paper but L-to-R mentally. 1 Quote Link to comment Share on other sites More sharing options...
Cake and Pi Posted January 1, 2016 Share Posted January 1, 2016 I had a mini-freak-out when we got to multi-digit subtraction in RS the first time, lol. I even posted about it (different board). After getting some reassurances, I went ahead and taught just as RS suggested, and it worked out very well. We were using 1st edition, which has a slightly different method than 2nd edition. They both go left to right, but 1st edition has you underline the number being traded from and no other marks and you do all the trading (underlining) before beginning subtracting, 2nd edition has little 1's written next to the number you trade to and no other marks and you think about saving a number for trading at each place value. I prefer the way we learned in 1st edition. 1st edition had a whole lesson on how you COULD do multi-digit addition from either direction, it's just easier from right to left because if you go left to right you have to erase after you trade. So when we did multi-digit subtraction, DS#1 made the observation that you can subtract in either direction as long as you do all your trades first. We did a few problems both directions and he declared that he liked doing it left to right better, so that's what he does! But DS#2 seems to prefer right to left (he's still doing the trading first and underlining). 2 Quote Link to comment Share on other sites More sharing options...
ScoutTN Posted January 1, 2016 Share Posted January 1, 2016 (edited) Yes, the left to right freaked me out a bit at first. But with some encouragement from here I taught it that way first and my Dd prefers it. I do too, now. I am faster left to right than with the traditional algorithm. I agree with the pp about the variation in 1st and 2nd editions. There are lots of you tube videos and Khan academy ones of the left to right. I watched a few to hear their explanations for why it is good because I didn't feel comfortable with it with only the explanation in the RS book. Edited January 1, 2016 by ScoutTN 1 Quote Link to comment Share on other sites More sharing options...
Squawky Acres Posted January 1, 2016 Author Share Posted January 1, 2016 I will plan to watch some of those YouTube and Khan Academy videos for reinforcement of the RS left-to-right method. It seems that this approach is worthwhile to teach, but that I don't need to insist on it if my son prefers the other way. I do like that it will reinforce the concepts behind multi-digit addition and subtraction so that they are not just applying a rote formula and sticking little ones on top of columns just because the math program said so. 1 Quote Link to comment Share on other sites More sharing options...
mamamoose Posted March 16, 2016 Share Posted March 16, 2016 They teach it left to right because its easier for mental math and RS is big on mental math, which is why I love it and also why I hate it! hahaha... My son is struggling with the mental math part of subtraction. I actually just searched right start math because I am finding it frustrating--not enough practice on paper, and I just plain out don't have time for all the stinking games right now!!!! I wish wish wish they had a supplemental workbook! I never thought of trying to find video...any videos out there someone has saved and would be good for the kiddos to watch? Quote Link to comment Share on other sites More sharing options...
Squawky Acres Posted March 16, 2016 Author Share Posted March 16, 2016 Thanks for reviving this thread! By way of an update, my children are happily subtracting left to right for mental math, and right to left (the normal way) for long multi-digit subtraction on paper. This morning, my second grader actually begged to do the additional problems on the page (that were not assigned in today's lesson) because it is "SO INTERESTING!" 1 Quote Link to comment Share on other sites More sharing options...
cmarango Posted March 16, 2016 Share Posted March 16, 2016 It doesn't matter which way your children subtract: if they are more comfortable going right to left then continue with that. I'm another person that really likes left to right once I figured out how to do it that way. Oh, and it's not a new thing at all. Quote Link to comment Share on other sites More sharing options...
ScoutTN Posted March 17, 2016 Share Posted March 17, 2016 They teach it left to right because its easier for mental math and RS is big on mental math, which is why I love it and also why I hate it! hahaha... My son is struggling with the mental math part of subtraction. I actually just searched right start math because I am finding it frustrating--not enough practice on paper, and I just plain out don't have time for all the stinking games right now!!!! I wish wish wish they had a supplemental workbook! I never thought of trying to find video...any videos out there someone has saved and would be good for the kiddos to watch? MM website has good, free worksheets. :) http://www.homeschoolmath.net/worksheets/ Quote Link to comment Share on other sites More sharing options...
Haiku Posted March 17, 2016 Share Posted March 17, 2016 Would I be doing RightStart all wrong if we subtracted ones first? I do like the rest of RS Level C, but have just run into this one problem. You'll be fine. I initially disliked the way RS taught subtraction because I was taught the standard algorithm, but I taught my dd the RS way anyway, and she's not had any problems at all. It's not better or worse; it's just different. It's not like the lattice multiplication method, which may be useful for showing why it works but is unwieldy and impractical for regular multiplication problems. The RS subtraction method is practical for any kind of multi-digit subtraction problem. I will say this: I switched my son from RS after B, so he learned to subtract with borrowing. Given his difficulties with handwriting, I wish he had learned the RS way. It would have made his work much neater and less visually confusing for him. Quote Link to comment Share on other sites More sharing options...
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