Signed numbers (or integers) are based on a number line. Positive (+) numbers mean moving right or
up on the line and negative (-) numbers mean moving left or down on the line. Before you can perform operations with signed numbers, there are a few things you need to know:
If there is more than one sign in front of a number, you may need to change signs. Follow the examples. Two negative signs cancel each other out. 3 – (­5) turns into 3 + 5 ­ (­1) – 4 turns into 1 ­ 4 One negative and one positive in front of a single number always leaves it negative. 9 – (+7) turns into 9 – 7 ­5 + (­3) turns into ­5 ­ 3 Think of adding and subtracting like combining numbers. Here are the rules to make it simple: RULE 1 ­­ If the signs of the numbers are the SAME, then ADD the digits and keep the sign of both. RULE 2 ­­ If the signs of the numbers are DIFFERENT, then SUBTRACT the smaller from the larger and keep the sign of the larger. Examples of RULE 1: Examples of RULE 2: ­ 5 + (­6) = ­11 7 + 2 = 9 3 – (­ 4) = 7 5 + (­2) = 3 ­3 + 9 = 6 ­10 + 6 = ­4 Multiplication and Division RULE ­­ If the signs are the same, the answer is positive. If the signs are different, the answer is negative. Examples of this RULE: (­2)(+3) = ­6 ­54 / ­9 = 6 (­5)(­4) = 20 ­4 / 1 = ­4 Now try some on your own and see if your answers match up: 1. 2. 3. 4. ­3 + 8 (5)(­2) 56 / ­7 ­3 – (­4) 5. (14)(2) 6. 15 – 5 7. ­90 / ­10 8. ­4 + (­7) 9. (4)(­3)(­2) 10. 6 – (­2) + 7 11. 5 – (­4) – (­8) 12. (­7)(­2)(­3) (Answers: 1. 5, 2. ­10, 3. ­8, 4. 1, 5. 28, 6. 10, 7. 9, 8. ­11, 9. 24, 10. 15, 11. 17, 12. ­42)