My DD6 is doing Addition Flash Cards. Here's her thinking.
9+5=?
so 5+5=10 and 4 left over from 9,
so 10 + 4 = 14


With 9 addition it's always one less than number added.
She doesn't want to hear the short cut and got mad at me for suggesting it. I didn't want to insist and just said there is more than one way to get an anwser. Why would she choose the long way? She is doing great with her + & - facts. I wonder about this. I feel like there is something happening that I don't get. Her brother DS9 is doing something with his 4 digit to complicate his computation too. Both are gifted kids. DS is probally hG or PG in math. Am I overthinking this? Please offer suggestions. Thank you in advance.

FWIW, your DD's way sounds as though it could be just as quick as the way you think she should do it, to me! I wouldn't sweat it, other than maybe to share how you did something in an "isn't it interesting that there are different ways to get the same answer" way. My DS will sometimes answer from one calculation and then point out another way, adding "so it makes sense", and I think that's to be encouraged. If one way really is faster than another, I expect it'll be the one adopted in the end....

I use your daughter's way for adding 7s and 8s, and your for 9s. It's especially good for subtracting. I think that she probably like to see problems in an abstract way, and just doesn't like 'techniques' as much as the elegance of actually understanding the basis of what she is doing.

As long as she is fast enough for the classroom, I would leave it be.

Smiles,
Grinity

My DS8 would add like this, especially when we first started giving him two digit numbers. He would explain how he got the answer and it always seemed complicated to me. I never worried too much though, since a) he was coming up with the correct answer and b) I thought it was a good thing that he made simple things more challenging since it gave his brain a work out it never got in school.

My DH is always advocating the subtract 1 rule when dealing with 9. I keep working on the "know by heart" method, since that is easier for me

When I add multiple digit numbers I like finding all the 10s first. So I use both techniques...

Yes, I think you are overthinking this

The program that my DS originally started in was called "rightstart". That program teaches math the way your daughter does it. breaks everything down into block of 5's and 10's. It creates a great environment for mental math later on. Sounds like your DD has already figured that out!

She is doing the right thing. That's how I was taught and that's how Singapore math is done.

Yeah, I was just going to second that her methos follows the rightsmart math program. We are using that now. As for complicating math problems, my ds6 does that all the time. If I tell him the most straight-forward method, he says it's boring and wants to do it his own way. We had an issue with this today with addition and subtraction. I suggested using his fingers at one point, and he wouldn't hear of it. I held up my own fingers, and he almost went through the roof! LOL

What your daughter is doing is decomposing numbers. It shows great understanding of number and flexibility in her thinking. If you think about it, she's already figured out how "carrying" works--and why! It's sort of like emptying a coin jar and totaling up the contents--we usually don't count coin by coin or grab random amounts to add together, we group them into "easy sets" for counting. To use your example, imagine that your daughter slid nine dimes across the table, then slid over another five--she's recognizing that one of those dimes will complete her "first set" and leave her with an extra four.