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Double digit addition


Slipper
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Honestly, some days I think things are going great and other days I just want to pull my hair out.

 

DD7 enjoys math. She's been asking me to teach her multiplication. I told her we couldn't go there until she is better at addition/subtraction.

 

Tonight, I said something about 16. She immediately told me that 16x2 equals 32 (along with a request to learn multiplication). I asked her how she knew that 16x2=32 and she told me that she heard me say once that 15 + 15 equalled 30. So, 16 was one more than 15 and there were two 1's which made 2. So, two 15's that equalled 30 and add 2 would make 32.

 

If she can do that, why can't she tell me 14 +3? Or 15 -2?

 

What am I missing? I feel like I have not taught her something key that would make all of this make sense. As it is, she shuts down when she sees the problem and immediately tells me that she can't add that high.

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DD7 enjoys math. She's been asking me to teach her multiplication. I told her we couldn't go there until she is better at addition/subtraction.

 

Why? My oldest figured out multiplication at age 5, before he knew his facts and before he knew how to add/subtract multi-digit numbers. Not a big deal. Teach her multiplication if she wants to learn it. :)

 

 

Tonight, I said something about 16. She immediately told me that 16x2 equals 32 (along with a request to learn multiplication). I asked her how she knew that 16x2=32 and she told me that she heard me say once that 15 + 15 equalled 30. So, 16 was one more than 15 and there were two 1's which made 2. So, two 15's that equalled 30 and add 2 would make 32.

 

Great! She's thinking a lot like how Singapore teaches. ;)

 

 

If she can do that, why can't she tell me 14 +3? Or 15 -2?

 

 

Some kids have an easier time with harder problems than easier problems. Strange, I know.

 

Maybe move on to multiplication for a short bit, then come back to these addition problems with a fresh mind. Sometimes if you've been at a topic for too long, it just gets frustrating and they need to take a break from it and let the material simmer a bit.

 

What methods have you used so far to teach problems like the above? Maybe someone here can give you an alternate method that you haven't tried yet. I see you use MUS, and I have no clue how they teach this, so I'm not much help. I used Math Mammoth for this type of problem, and I can't even remember how that program taught it. :lol:

 

But please do let her learn multiplication if she wants to learn it! That's not a topic that has to wait until she's older. And who knows, it might even help her get over this hump!

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Thanks. :) Currently I have used manipulatives for addition, including the ones sold by MUS. There seems to be a disconnect once we get to the teens. But, if 3 blocks and 3 blocks is six blocks, then why doesn't she understand that 13 blocks and six blocks is nineteen?

 

Then, I thought that perhaps times tests and drills would just help her cement the information. But, that doesn't seem to help either.

 

She hates repetition.

 

She enjoys it most when I find worksheets off the internet. She asks to skip math and go straight to her 'challenge math sheets'. I've already decided to go to Singapore next year and I'm also doing Beast Academy with her. She is going nuts over 'comic book math' which I'm hoping will motivate her to work towards the problems in that book.

 

Thanks for suggesting that she should go ahead and try multiplication. My husband has also been saying that (he's the kind of genius who is scary smart but can't tie his shoes and talk at the same time lol). I just don't want to confuse her.

 

Thanks again for taking the time to answer.

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My 7 yo daughter is currently about to finish Math Mammoth Addition/Subtraction 2A. She does understand the addition and subtraction you're talking about, but I've noticed that doing it in the teens, as opposed to the higher tens (20s, 30s, etc.) confused her more. I'd say now she's about on equal ground in all the 10s, but that took a few months, I'd say. I never particularly focused on it, but when it came up, took a little time to go over it and compare it. I'm not sure why the initial confusion, but I will say that I'm pretty sure there was a bit of anxiety as well when she would see a problem with the teens.

 

As I noted, this probably doesn't help you at all, but if you notice an especially freaky aversion to the teens, you might want to focus on something NOT teens.

 

Good luck!

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Thanks. :) Currently I have used manipulatives for addition, including the ones sold by MUS. There seems to be a disconnect once we get to the teens. But, if 3 blocks and 3 blocks is six blocks, then why doesn't she understand that 13 blocks and six blocks is nineteen?

 

Are you using 13 individual blocks or a ten rod and 3 units? I'm wondering if the concept of place value is shaky? :confused: Though I thought MUS was supposed to be good for teaching place value.

 

Unfortunately, it's been a year since I taught this topic, and DS1 didn't have any problem with it. DS2, we'll see about. He tends to do weird stuff like that too, and I never have any clue what's going on in his head. Cuisenaire rods have caused him to really take off in math (I suspect he thinks in pictures and now has those rods in his head to do math with... I've seen him "count objects in his head" rather than counting fingers or actual objects... it's a bit weird to watch, especially when the child hasn't been adding for very long). He doesn't yet know how to do this type of problem, as we're still adding numbers 10 and under. The closest thing he's seen is something like 10+4. I have been hammering place value into his head though, as we use a 100-chart, straws, and money. He couldn't count much past 10 just a few months ago, and recently he wrote numbers to 40 (filling out the February calendar... um yeah, February is really long this year :lol:). It's been a slow process for the place value stuff, but it's working. I see the light bulb going on. ;)

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I have used 13 individual blocks and that may be the problem. It's interesting that you mentioned that about place value because I was testing her today (placement type tests looking towards next year) and made a note to work on her place value. I don't think that has 'stuck' yet either. I'll cancel this week's math work and focus on place value and see if that helps. Thanks :)

 

Marie, thank you. :) That makes me feel better.

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I definitely would work on place value and use the tens rod as suggested. It's the only thing that helped my DDs get the concept of the teens. In the MUS video/IG he does mention kids have the most trouble with the teens because it doesn't follow the normal pattern of the tens. My youngest DD used his onety cheat until the teens made sense to her (I think it was a week or two). It drove me batty to hear her count that way, but she's good now with the regular teen counting. I have to admit I was afraid the onety business would become permanent, but once she got it she happily swapped to the -teen system.

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I have used 13 individual blocks and that may be the problem. It's interesting that you mentioned that about place value because I was testing her today (placement type tests looking towards next year) and made a note to work on her place value. I don't think that has 'stuck' yet either. I'll cancel this week's math work and focus on place value and see if that helps. Thanks :)

 

Oh yes, definitely use the 10 rod for anything greater than 9. :D Hopefully a week of focused place value work will get her going. Do let us know how it goes!

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I started my dd5 on Multiplication recently. I was surprised when I saw it so early in her Miquon math books. But my dd LOVES it. I did a rather wordy post about adding it in so early and how much I think it helps her. It has renewed her interest in math... Honestly I think she was getting bored with all the addition and subtraction. She does not have all her math facts memorized yet but - boy- does she like multiplying. :)

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I would teach her what Right Start calls "part-whole circles" and what Singapore calls "number bonds". What you do is to draw a big circle with two smaller circles underneath connected to the big circle by lines. The total goes into the top circle and the two parts go in the smaller circle. See here for a visual.

 

13 would be whole and the two parts would be 10 and 3. If the student knows that 3 + 6 = 9, then it is obvious that 10 + 3 + 6 = 19.

 

My DS is currently working on adding two double-digit numbers. He has not yet learned the traditional algorithm but he can solve the problems using part-whole circles.

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