Dd12 and (bad) negative numbers :)

[Night Elf]

Dd12 thinks negative numbers should be banned from all math programs. :tongue_smilie:

 

How do I help dd12 understand that when subtracting negative numbers,

 

-5 + (- 3) is the same thing as -5 - 3 or,

5 - (-3) is the same thing as 5 + 3

 

She is doing well with all the other concepts in MUS preAlgebra so far. It is just subtracting negative numbers that is throwing her for a loop, especially when the problem starts with a negative number.

 

Any suggestions?

[Sputterduck]

If she thinks those should be banned, wait til you get to imaginary numbers. I almost boycotted the test and homework for those... But that's because my best friend's mom told me she did when she was in school. lol

 

If it's imaginary, then don't waste my time with it!

 

(Yes I see the point now that I am adult)

[Sputterduck]

Have you tried a number line?

[Mrs Mungo]

Dd12 thinks negative numbers should be banned from all math programs. :tongue_smilie:

 

How do I help dd12 understand that when subtracting negative numbers,

 

-5 + (- 3) is the same thing as -5 - 3 or,

5 - (-3) is the same thing as 5 + 3

 

She is doing well with all the other concepts in MUS preAlgebra so far. It is just subtracting negative numbers that is throwing her for a loop, especially when the problem starts with a negative number.

 

Any suggestions?

 

Use money.

 

I owe mom 10 dollars. I have a net worth of -$10. I get paid $30. I now have a net worth of $20 because $30 + (-$10) = $20. Mom agrees to allow me to pay in installments, so that I can buy some other things. I pay her $5. She subtracts $5 from my debt. (-$10) - $5 = -$5

 

Does that help?

[specialmama]

Along the same line as a number line: I really struggled with this as a student as well. What helped me was seeing the number line drawn on a thermometer.

[Night Elf]

I've tried a number line and the concept still didn't click. I love the idea of the number line on a thermometer though. Hm..

 

I tried money, but not the idea of installments to watch the number get up to a positive. I'll try that too.

 

And imaginary numbers? :scared:

[Sputterduck]

And imaginary numbers? :scared:

 

Yes. Terrible things I tell you. I think some theoretical mathematician came up with them to torture students by making work with things that don't exist and don't matter.

 

That said, they are easy, not hard at all. But the torture of making myself do something imaginary was terrible.

[Suzanne in ABQ]

I've tried a number line and the concept still didn't click. I love the idea of the number line on a thermometer though. Hm..

 

I tried money, but not the idea of installments to watch the number get up to a positive. I'll try that too.

 

And imaginary numbers? :scared:

 

 

Try putting a number line on the floor with tape. Tell her that subtracting means to turn around and go the other way. AND, negative numbers mean that you turn around and go the other way. Then, have her literally walk the number line.

 

For 3 - 5, have her start at 0, and move three tics in the positive direction, then turn around and move 5 tics in the opposite direction.

 

For 3 - (-5), have her start at 0 (again) and move three tics to the positive, then have her turn around and face the opposite direction for the "minus" (but don't move yet). Then, have turn around again for the negative sign on the 5, and finally move 5 spaces (which will now be in a positive direction).

 

Keep doing it with different combinations of numbers and signs, until she gets it. I imagine she'll think this is pretty fun, and it will give her a great feel for what negative signs do to numbers.

[Ellie]

Dd12 thinks negative numbers should be banned from all math programs. :tongue_smilie:

:iagree::iagree::iagree:

 

Negative numbers are evil. When I'm reading about them, I feel like I'm reading the instructions for that card game in the original Star Trek show. :confused:

 

How do I help dd12 understand that when subtracting negative numbers,

 

-5 + (- 3) is the same thing as -5 - 3 or,

5 - (-3) is the same thing as 5 + 3

 

See, that just makes no sense to *me* at all. Your dd and I must be kindred spirits.:D

 

She is doing well with all the other concepts in MUS preAlgebra so far. It is just subtracting negative numbers that is throwing her for a loop, especially when the problem starts with a negative number.

 

Any suggestions?

 

I don't believe there's any way to help her understand. There is no understanding. ::looks for the banging-head-on-keyboard smilie::

 

OTOH, millions of people successfully complete algebra and seem to understand those pesky negative numbers. I guess your dd and I are the ones out standing in our field.:D