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Help with integers! Rules for + and -


Senior Member
Our math book is horrible! I haven't taught this before, new to 5th grade, and the way I learned it is different from the book but I know there are some rules. Anyone have a list of tried and true rules for adding and subtracting negatives and positives?


Senior Member
I found some :)

Anyone have anything else? This makes sense to me, different than how I learned but I think the kids will understand this way better than the way the TE says to teach them.


If the signs are the same then you add the two numbers and keep the

Ex. 6 + 2 = 8 or -6 + -2 = -8

If the signs are different, subtract the two numbers and take the sign
of the larger number.

Ex. -6 + 2 = -4 or 6 + -2 = 4


Change the sign of the second number, then add the two numbers using the
rules for addition, above.

Ex. 6 - 2 = 6 + (-2) = 4
Ex. -6 - -2 = -6 + (+2) = -4
Ex. -6 - 2 = -6 + (-2) = -8
Ex. 6 - -2 = 6 + (+2) = 8

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Senior Member
Interesting- thanks for posting that!

We do not get into it too much in 5th grade here (not a standard, I do some extra things in math just to help prepare them for 6th grade though, and this is one of them), but I always start out by using a number line and jumping around (like you do in 1st grade sometimes when you learn to add). Like you start at 5, and if you add a -6, you jump backwards 6.... I like those rules you posted. I think it might confuse the heck out of my kids (this group seems easily confused this year), but I might try it anyway ;)


Senior Member
I'd really recommend you use number lines so you teach kids the concept, not just a rule they don't really understand.

If the number line has negs and positives, you can act out any problem.

6 - -7

Start at the 6, take away moves backward, but the -7 tells you to do the opposite and you land at 13.

-5 + 8

Start at the -5 and add (move forward) 8...end at the 3.

-4 - 9

Start at the -4 and subtract (move backward) 9...you land at the -13.

9 + -4

Start at the 9...adding moves forward, but the - sign tells you to do the opposite. You land at the 5.