number lines in kindergarten b math

[queenireneof3]

Hello...

Simple question here! My daughter is in Singapore Kindergarten B math. So far it has been great. She is doing well and comprehending everything and always looks forward to math. (My oldest son is in singapore 1b and has always struggled.)

Anyways, we hit a small bump with adding and subtracting on the number lines that I am tempted to ignore, but since i know everything is important in Singapore, i would like some advice for how to teach the number lines.

The concept is obviously simple, count up on the number line for addition and count backwards for subtraction. But crossing off for subtraction makes much more sense to her (and me!) so I have allowed her to do that. That means crossing off the number we are starting with when subtracting. For example. 7-2= She would cross off 7 and 6 and see that there are five left on the number line and know that 5 is her answer. Today I was trying to teach her how to count backwards on the number line to subtract, but I think the difference between that and crossing off are too complex for her.To count backwards, 6,5 she would assume the answer is 4. Does that make sense?

I saw her shut down in math for the first time today and want to quit because she couldn't get the number line. Now I am worried that I should have let her continue to cross off instead of trying to teach her to count backwards. I don't know how important that is? She could probably do 7-2 in her head, but I think I might be confusing her with the number line. I am hoping to avoid the serious struggles I have with my older in math. Can I allow her to cross off the number lines instead of bouncing back? It makes way more sense to me to cross off as well.

[TrueGRIT]

My son has always worked better by crossing the numbers off. Sometimes I let him. Other times I taught him to count back by pointing with the pencil. If the dot ended on a number, that was the answer. So, using your example 7-2 he would make a small pencil dot on 6 and count "1", then make a small dot on 5 and say "2". He then knew the answer was 5. 7-2=5
It took a bit but was less frustrating and he finally got it.
Don't know if that would help. Just wanted to throw it out there for you.

[Gwenny]

I don't know what it looks like in Singapore, but with my olders, we always put the pencil on the number you are starting with (7) and then drew a "hop" down 1 and then another hop 2 to land on five. (looks like a half circle)

[StephanieU]

We also aren't using Singapore, but here is an idea to "build up " to subtraction on the number line. Take some sort of cube (Lego, Unifix, snap, etc). Use that as your "unit" for the number line. You probably will have to draw a big one on paper to fit the size. Then build the first number. So, if it was 8-3, make a stack of 8 cubes. Lay this on the number line to show that it is 8 long. Then break off the 3 cubes (one at a time if that is how Singapore does it). Show what you are doing on the number line. It will be similar to crossing things off probably in her head and show how the number line is very similar yet different.

[raindrops]

We also aren't using Singapore, but here is an idea to "build up " to subtraction on the number line. Take some sort of cube (Lego, Unifix, snap, etc). Use that as your "unit" for the number line. You probably will have to draw a big one on paper to fit the size. Then build the first number. So, if it was 8-3, make a stack of 8 cubes. Lay this on the number line to show that it is 8 long. Then break off the 3 cubes (one at a time if that is how Singapore does it). Show what you are doing on the number line. It will be similar to crossing things off probably in her head and show how the number line is very similar yet different.

I was going to suggest something like this, but I was going to say use goldfish crackers above the numbers. LOL. Food always helps.

[MelInKansas]

In one of the guides there was the activity where you make a number line on the floor with tape and then you drive a car on it. This really clicked for my 7YO when she did that. She loved it and played it for quite a while. So you put the car on your number, and drive to higher numbers if adding, to lower numbers if subtracting. Counting to the number you are adding or subtracting (rolling the car to the next number as you count). She loves the crossing off too but that one really helped her use the number line.

So I don't think the point is that she needs to be able to count backwards right now. Just that she can see on the number line how subtracting is going down in numbers and adding is going up. It's a slightly different idea than the adding to and taking away. It's looking at things slightly differently to help them understand. I don't think my kids could count backwards when they were doing K math, it was just some exposure to the idea of counting backwards.

[queenireneof3]

Thank you! I think the issue comes with when she crosses off the numbers on the number line, the answer is always the next one down. However when counting backwards on the number line, the answer is the one you land on. So knowing the difference between when it is the number she lands on and when it is the one below the last one she crossed off is too complicated for her it seems. I think we will try the number line with a car today and see if that helps. thank you!

[queenireneof3]

So here's what we did today that worked: I got out the tape measure and a cheerio. We worked through the problems in the workbook by bouncing the cheerio up and down the tape measure. I told her this was a different way than crossing off and she totally clicked with it today! Yay! I told her it was the bouncing method. ha ha! Thank you for all your input!

[MelInKansas]

Great! I'm so glad it clicked for her. I think just physically moving the car/cheerio is what makes it click for some reason.