Math Question

[mom23]

We've been using CLE math and my son is having a hard time understanding borrowing for subtraction. In looking at a couple of problems I was wondering if it would be okay to show him that some problems don't need borrowing? For instance, with 116-28 could I have him look at the 10's and 1's columns together and see that 16-8=8 and 100-20=80, rather than regrouping those numbers? Is this more of how Singapore would approach it? I realize he needs to understand borrowing, but some problems are easier without it.

[StephanieU]

I haven't used Singapore, but I have taught future elementary teachers math (at our community college). I have become a HUGE fan of pictoral/hands on introductions to things like borrowing. I would definitely have him draw pictures for a couple and see what is going on.
Do you have Legos? Work with something "small" so it isn't tedious like 24. That would be two towers of 10 legos and 4 extra legos. Then if you are to subtract 3 - you can just take away with those from the "extras." But, if you wanted to subtract 6, you have to break up one tower. That would leave you with 1 full tower and 14 "extras." Then take away with 6, and you have 8 extra left plus the tower (18). Once he does a few like that, he will probably get a better idea of why you "borrow" and what it is actually doing.
And if you don't have Legos or that type blocks, you can use graph paper to draw them. Or, there are websites with virtual manipulatives too.

[Motherjoy]

Carrie has written some good instructions in the Bigger guide for borrwing. Even though you are using CLE, you can check your Bigger guide to look up her instructions. He must understand why we borrow.

You sound like you are a mathy person, and that you easily play around with numbers in your head. My husband Is like that and he tries to teach that way to our children. The problem is that it can be confusing to kids if you try to throw in a lot of tricks when they already don't understand WHY something is happening in math. So, I wouldn't show him that trick until you're sure he understan borrowing. Get some math blocks (we use the MUS blocks with our Singapore math) and show him over and over again until he understands. Not all in one sitting, though. If he's getting frustrated, put it away for tomorrow.

[mom23]

Thank you for the suggestions! Today went much better than yesterday with it-it seemed to click and he actually thought it was kind of fun!?! We had spent a couple of days playing around with blocks and breaking them apart to borrow...that's when he really wasn't getting it, and especially wasn't able to translate anything to the numbers when we looked on paper. I'll take a look at the Bigger manual, though, and see what ideas there are. I didn't even think about that ! Yesterday I broke the numbers apart in columns, and something about that must have made it click, because today when we pulled it out he started showing me how to do it. One of these days I'm going to learn that this boy definitely has his maxed out points and it's not helpful to keep drilling it, but I've got to put it away for another day!

I had to giggle at being called a mathy person-thanks for the compliment, though! I've always hated math and had to learn so many tips and tricks to try to understand it! I definitely appreciate your advice to not bombard him with all those different approaches, though. I need to keep that in mind for sure. I guess I have this idea that if they don't get it that I need to present it another way until they do get it. Sometimes, all these other ways just confuse them more and it just takes time and exposure to new concepts.

[Motherjoy]

Well, I'm so not a mathy person. I got good grades in school, but only because I memorized the steps. I didn't even realize that I didn't understand WHY something worked. It wasn't until 7th grade that I looked up at the board and *lightbulb* I understood WHY we borrowed and carried and all of that. Seriously. So, I've been so careful with borrowing.

My 8yo just learned this a few weeks ago, and we had to work several days as well.

Now, when he's working a problem in his head I can see that he does exactly what you are saying, he switches numbers around until he gets his answer. Its neat to see his brain work that way, because I don't remember every thinking like that. I just followed the steps, you know? It sounds like you are doing a great job!