ondreeuh Posted February 9, 2014 Share Posted February 9, 2014 My son understands regrouping and can do it fluently with base-10 rods and with counters. He loves the games where you roll a die and either add on until you get to 50/100/ whatever, or count down to zero. He understands it all very well on a concrete level. When we play, I keep score and show how the traditional algorithm matches what we are doing with rods & cubes. However, when he is given the worksheet, he freezes, especially when there is a 2-digit minuend. (Or is it subtrahend? The number you are taking away.) So he can do 43-28 with rods & cubes, but not on paper. Should we park and practice this, or move on? I think it is retaught in 2A ... But he is in kindergarten and I am in no rush, so I don't mind pausing here for a while and working on clock or something. Those quarter hours are a little tricky for him. Part of this is perfectionism/anxiety; he often thinks he can't do something that he can do. Should I wait, or is it really ok that he uses manipulatives to solve these? Quote Link to comment Share on other sites More sharing options...
SKL Posted February 9, 2014 Share Posted February 9, 2014 My eldest didn't really get it at that age either. We went through it using manipulatives and heaved a sigh of relief when it was over. LOL. Come fall around Miss A's 7th birthday, it clicked when they were doing 3-digits with regrouping. Quote Link to comment Share on other sites More sharing options...
Monica_in_Switzerland Posted February 9, 2014 Share Posted February 9, 2014 I used rods right next to the vertical algorithm, so the rods would look just like the numbers in question. i.e. 25 2 ten rods 5 ones + 18 1 ten rod 8 ones ............. ......................................... Then do it step by step, first rods, then pen to paper. 1. Combine the ones and get 13. Oops, we can't have 13 ones in the ones column, so "glue" ten together and carry it over to the tens, lay it above the ten rods already out. Now how many ones? 3! 2. Write 3 in the ones column. Draw a little 1 in the tens column to represent the ten rod you just carried over. 4. Add the tens rods- 3 plus the one you carried makes 4! 5. Write 4 in the tens column. Similar idea for subtraction, except you would "unglue" a ten if you didn't have enough ones to subtract from. After doing just a step with the rods, show the same step on paper. Maybe that's what you're already doing, but if not, thought I'd throw it out there. I would not necessarily park there, but I would do a couple problems every day, even as you move on to non-dependant subjects like weight and measure, clocks, etc. Quote Link to comment Share on other sites More sharing options...
ondreeuh Posted February 9, 2014 Author Share Posted February 9, 2014 Yeah, he regroups with manipulatives on his own easily. He has place value down pat. I think it is just when he sees it on paper it is not as easy to see the process. Horizons math sets up problems vertically that you can count on/count back without regrouping, so he is used to doing those in his head. He doesn't need to start with the ones column first in those problems, so it kind of created a habit. I tried to make him always start with ones, but when the problem is 48-2, he just starts with tens instinctively. Quote Link to comment Share on other sites More sharing options...
sunnyday Posted February 9, 2014 Share Posted February 9, 2014 We just did a session on this. DS was getting confused and adding after regrouping, or subtracting the smaller from the larger digit when he should regroup, despite a scary good grasp of place value and composition/decomposition. We had a breakthrough by working through the pages in the Singapore IP that review all the strategies for two digit subtraction; and then also when he started to subtract the wrong digit I pointed out that 4-5 was not 1 but -1. Lightbulb! He easily added -1 to the remaining tens to get a solution! lol I am a fan of getting a firm foundation. For a child who needs less repetition that means hitting the same concept without making it feel repetitive; minimizing practice problems; interspersing new or familiar concepts with the sticky one. But not skipping it, IMO. Quote Link to comment Share on other sites More sharing options...
blondeviolin Posted February 9, 2014 Share Posted February 9, 2014 Yeah, he regroups with manipulatives on his own easily. He has place value down pat. I think it is just when he sees it on paper it is not as easy to see the process. Horizons math sets up problems vertically that you can count on/count back without regrouping, so he is used to doing those in his head. He doesn't need to start with the ones column first in those problems, so it kind of created a habit. I tried to make him always start with ones, but when the problem is 48-2, he just starts with tens instinctively. I'd just move forward. It's about exposure. Keep doing it with the rods and he'll move past needing the concrete. You might even see if you could have him draw the rods instead of pulling them out. (Squares for hundreds, lines for tens, dos for ones.) And I wouldn't get hung on whether he is adding tens or ones first. A lot of mental math is adding left to right and regrouping nearly simultaneously. As long as he's correct, I wouldn't worry. Quote Link to comment Share on other sites More sharing options...
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