rachelpants Posted April 10, 2016 Share Posted April 10, 2016 Just curious how Singapore teaches it. RS does left to right...it's not really coming naturally to DS so I'm considering my options. TIA :-) Quote Link to comment Share on other sites More sharing options...
vaquitita Posted April 10, 2016 Share Posted April 10, 2016 Singapore teaches mental subtraction left to right (566-235= 566-200, 366-30, 336-5) and also the right to left algorithm using pencil and paper. Hope that helps. 1 Quote Link to comment Share on other sites More sharing options...
athomeontheprairie Posted April 10, 2016 Share Posted April 10, 2016 I use rs. I taught it their way. Then I taught it right to left. You don't need to switch programs because of one concept. Teach it the other way if they need it. 2 Quote Link to comment Share on other sites More sharing options...
SparklyUnicorn Posted April 10, 2016 Share Posted April 10, 2016 No not really. Sometimes they break up the problem by place value and do it that way. Sometimes they showed some of it mentally. I do not recall left to right being heavily emphasized over right to left. 1 Quote Link to comment Share on other sites More sharing options...
rachelpants Posted April 10, 2016 Author Share Posted April 10, 2016 When the kids do subtraction problems on paper in Singapore they go right to left, but mentally it is left to right. Is that correct? Quote Link to comment Share on other sites More sharing options...
SparklyUnicorn Posted April 10, 2016 Share Posted April 10, 2016 When the kids do subtraction problems on paper in Singapore they go right to left, but mentally it is left to right. Is that correct? I can't for the life of me remember, but that seems highly possible. It is usually easier to do it left to right mentally. I did not get too hung up on it if my kids couldn't do all subtractions mentally. Sometimes it is easier to do it one way verses another way depending on the numbers. The SM methods aren't really that out there like people assume. 1 Quote Link to comment Share on other sites More sharing options...
rachelpants Posted April 10, 2016 Author Share Posted April 10, 2016 We've only done RS a-c I wonder if it ever teaches the standard algorithm in future levels. Hm. I agree that it depends on the numbers. Thanks! Quote Link to comment Share on other sites More sharing options...
Cake and Pi Posted April 11, 2016 Share Posted April 11, 2016 We've only done RS a-c I wonder if it ever teaches the standard algorithm in future levels. Hm. I agree that it depends on the numbers. Thanks! No, it sticks with left to right all the way through E (in 1st ed). My older two both learned subtraction the RS (1st edition) way. DS#1 has continued to do left to right, DS#2 seems to prefer right to left (thanks to playing Prodigy, probably), but he's not consistent. Sometimes he does right to left, sometimes left to right. He even changes in the middle of the problem sometimes! He'll subtract the thousands first, then the ones, then the tens and hundreds (or hundreds and tens, lol). As long as they do all the trades first and consistently keep place value, it doesn't matter what direction the subtraction is done in. It's the same with adding, btw. It doesn't matter what direction you add as long as you keep track of trades (and you may have to erase after you trade if you go left to right, but that doesn't seem to bother DS#2). Quote Link to comment Share on other sites More sharing options...
Kiara.I Posted April 11, 2016 Share Posted April 11, 2016 No, it sticks with left to right all the way through E (in 1st ed). In 2nd edition, I haven't found that to be the case at all. They suggest right to left for written. Starting in....B? Anyway, you can absolutely suggest whatever direction you like to your student. OP, are you using first or second edition? Quote Link to comment Share on other sites More sharing options...
Cake and Pi Posted April 11, 2016 Share Posted April 11, 2016 In 2nd edition, I haven't found that to be the case at all. They suggest right to left for written. Starting in....B? Anyway, you can absolutely suggest whatever direction you like to your student. OP, are you using first or second edition? To clarify, in 1st edition 4-digit addition on paper is taught right to left (also starting in B) just like in 1st edition; however, there is at least one lesson prior to them officially introducing the algorithm where kids are allowed/ invited to go left to right -- so they can experience how it does in fact work, but is cumbersome since you have to erase if you make a trade. I don't recall there being a lesson like that in 2nd edition though. So, yes, addition is taught right to left (starting in B), while subtraction is taught left to right (starting in C). We did A-E (all the elementary levels) in 1st edition and A-C in 2nd edition (and then switched back to 1st edition) and subtraction stayed left to right throughout. The traditional right to left for paper subtraction was never taught. But, my point was that it doesn't matter. Quote Link to comment Share on other sites More sharing options...
pkbab5 Posted April 11, 2016 Share Posted April 11, 2016 Yes in Singapore Math 2A & 2B it is as someone already mentioned - left to right when doing mental subtraction, and right to left when doing written subtraction. Quote Link to comment Share on other sites More sharing options...
rachelpants Posted April 11, 2016 Author Share Posted April 11, 2016 Super helpful! Thanks everyone! :-) Quote Link to comment Share on other sites More sharing options...
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