Question

Can someone help me understand how to add and subtract negatives and positives?

Answer 1

Okay, as you know, adding a positive and a positive gives you a bigger positive number. e.g 21 + 19 = 40.

Subtracting a positive from a positive might give you a negative number or a smaller positive number. e.g 21 - 19 = 2 or 20 - 24 = -4. That's simple, we all learned this! :)


Adding two negatives (e.g -4 + -5) will always give you a negative number. To make it easier, just think of the numbers only (4, 5), add them together, and then just put a negative sign by the answer (e.g 4 + 5 = 9 so put - to make -9).

Subtracting two negatives can be a bit tricky! When we say, for example, -5 - -4, we must turn the negative number that was to the right of the minus ( -4) into a positive number! So now it becomes -5 +4 ! And then you get your answer. (which is -1).


Adding a positive to a negative can give you a positive or a negative answer. It just depends which number is "bigger". E.g -20 + 31. << 31 is the "bigger" number, and it is a positive, so we know that our answer will be positive. E.g -20 + 9. << 20 is the "bigger" number (even though it's a negative but forget about that) and it is negative, so we know that our answer will be negative.

Adding a negative to a positive can give you a negative or a positive answer. Like I said, it depends on which number is "bigger". e.g 20 + -9 . We can just remove the + sign and it now becomes 20 -9, which is easier to understand. 20 is the bigger number, and it is positive, so we get a positive answer. e.g 20 + -30 becomes 20 -30 and -30 is the "bigger" number and it is negative, so we'll get a negative answer.

Subtracting a negative from a positive does the thing I mentioned earlier: e.g 20 - -9. The -9 is right of the minus sign and becomes positive: 20 +9! :)

Subtracting a positive from a negative, like I said, depends on which number is "bigger". e.g -30 - 9 (we know 9 is positive even though we don't show the + sign).  Now, to make it simple, just block out the - sign by the 30 so it becomes 30 - 9. You know what that answer is: 21. But because -30 is "bigger", and it is a negative number,  the answer will be negative so it's -21. E.g -30 - 42 <<  Block out the - sign by the 30, and 42 is the "bigger" number, so the answer will be a positive. Just look at the difference between "bigger" number and the smaller number (without signs) . That'll give your answer. 42 - 30 = 12. 42 was the "bigger" number and a positive, and we looked at the difference. :)