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Need help w/negative numbers

K in MI

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You could try using a number line as an illustration.


5 + (-3) Start at 0, use a blue pen and move 5 units to the right. Then use a red pen and move 3 units to the left. You end at 2, so 5 + (-3) = 2.


-2 + (-4) Start at 0, use a red pen and move 2 units to the left. Then move 4 units to the left. You end at -6.


I got a white board number line at Rainbow Resources and with white board markers, you can do a lot of arithmetic problems without the frustration of constantly redrawing the number lines.


For addition, you can also say to think about positive numbers as money you have and negative numbers as money you owe.

So if you have 5 + (-3), you had five dollars but spent 3, so you still have 2.


With -2 + (-4), you owed two dollars and borrow 4 more, so your situation is that you owe 6, thus -6.


For subtraction, at this stage, I'd use the rule that a - b = a + (-b) and rewrite every subtraction problem as an addition problem.


I also usually like the explanations on purplemath. Here's their integer approach: http://www.purplemath.com/modules/negative2.htm


Hope this helps some. Good luck!

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