How to do negative equations like 1-10=? using cuisenaire rods?

[enrich]

My DS is thoroughly enjoying the Orange workbook in Miquon. He tries to come up with his own equations and solves those problems instead of doing the workbook problems. Yesterday, he asked me how to do equations like 1-10, 2-10, etc using cuisenaire rods. I checked the Lab annotations book and I don't see it covers negative numbers. Can someone explain to me how to do negative number solutions using the rods?

[boscopup]

I have no clue, so this is mostly a bump. I used a number line to teach adding/subtracting negative numbers. So far, both of my older two have understood it with a number line at 5 years old. I think the number line is great to use for negative numbers.

 

I'm thinking with base 10 blocks, they usually use different colors to demonstrate it?

 

Oh... thinking while I type... If you place your rods next to each other going the other way, the hole you fill in would be the negative number. Let's see if I can draw that...

 

2-10:

...........[--]

[----------]

 

Line them up like that, and whatever goes in the hole, that's the amount below zero. So you stick your 8 rod there, and it's -8.

 

I still think the number line would be best to demonstrate first, because with the C-rods you can't tell if it's + or - 8.

[nansk]

:bigear:

 

I'd like to know too.

I have used the stories & lessons from CSMP, using two coloured glass beads, one for positive, one for negative.

[TKDmom]

Miquon number lines a lot in addition to the c-rods. I would probably focus on using a number line to teach negative numbers. The rods don't lend themselves well to negative numbers, which are the absence of a number rather than a physical thing.

 

The only thing I can think of is to use a debt/lending analogy using the c rods. Like, "you need to pay me a ten-rod, but you only have a one-rod. How many do you still owe me?" and let him use the rods to see the difference.

 

Or maybe you could make some paper strips in c-rod lengths to show the "holes" where you would have a negative number.

[Rosie]

I'm going to make videos on this eventually. They will be here...

 

https://vimeo.com/educationunboxed/channels

 

... but for now, you might want to check out Crewton Ramone's videos. Mine will just be replicating what he does, just with C-rods. I'm going to put a thin strip of tape along one side of each C-rod to represent the negative of that number. His blocks actually have a "negative" side.

[Heathermomster]

I take a black marker and run it down one side of the rod we are using. The finish on our rods is in good shape, so the color rubs off easily when we are done. I've only done this with the lighter colored rods. The tape "along one side of the rod" idea is excellent.

[nrself]

Cool. More websites to read. :)

 

Thanks for the post.

Nicole

[Dmmetler]

You can get rod tracks that have positive and negative numbers.

[Spy Car]

We played around with this a little (although my son just "got" negative numbers pretty easily).

 

What I did was to make a graph that was more akin to stretched out thermometer that worked vertically (rather than a horizontal number-line). So in this case one would go "up" 1-Unit from zero in a positive direction, and then (from positive 1-Unit) go "down" 10-units and end up at (-9) using the rods.

 

For some reason the "vertical" orientation seemed better for us, not that it should really matter.

 

Zaccaro's section on negative numbers in Primary Grade Challenge Math was helpful.

 

Bill

[Spy Car]

ETA: Slow memory recall this morning, but we also played a game (not using rods) using playing pieces on a regular time-line (negative-zero-positive) where we would roll two ten-sided dice. The first die was the minuend and the second the subtrahend. One found the difference and moved positively, negatively, or stayed put accordingly.

 

It is a good game.

 

Bill

[mommymilkies]

I don't use c-rods. But I do use regular cm cubes and rods. I teach them it's like Mommy's bank account. If I have $2 and then I write a check for $10, I owe the bank (the kid) $8. They like it in money terms-especially when I talk about me owing them money. :tongue_smilie:

[happypamama]

I take a black marker and run it down one side of the rod we are using. The finish on our rods is in good shape, so the color rubs off easily when we are done. I've only done this with the lighter colored rods. The tape "along one side of the rod" idea is excellent.

 

Love that idea!

 

I introduced negatives to my daughter in the sense of owing money. That did it for her. For my son, the number line helped, but I also have some flat bars, similar to C-rods, only smaller and flatter; I think they are actually designed for overheads. They're clear red and clear yellow, and I designated one negative and one positive. That showed my son how a red and a yellow cancel each other out and make zero. That got it for him.

[melmichigan]

Do C-Rods have an empty underside? That's how we do them with MUS blocks.

[crazyforlatin]

Do C-Rods have an empty underside? That's how we do them with MUS blocks.

 

No. So is that why MUS blocks are empty on one side - for negative numbers? I don't have these blocks.

[besroma]

:lurk5:

[crazyforlatin]

What about using a piece of paper that has a line down the middle - one side with a positive sign and the other side with a negative sign? You can still use c-rods, and I think it might provide another way of lookng at integers from a different perspective than just using a number line (eg. go left first but really go right due to the negative integer in 5-(-3)). I haven't taught DD that 2 negative signs mean a positive - seems too procedural. It would be better for her to realize that on her own.

 

Also, still using c-rods, and I just tried this today, is having the subtrahend over the minuend, so whatever sticks out is the answer. However, it's a limiting method and DD and I both found it better to use the paper method.