 Signed Numbers MathBitsNotebook.com Terms of Use   Contact Person: Donna Roberts   Adding Signed Numbers:
 When adding two numbers with the same sign,      1. add the absolute values, and      2. write the sum (the answer) with the same sign as the numbers. • (+4) + (+7) = +11 • (-5) + (-8) = -13 • (4) + (6) = 10 When adding two numbers with different signs,      1. subtract the absolute values, and      2. write the difference (the answer) with the sign of the number having the larger absolute value. • (+5) + (-8) = -3 • (-10) + (+15) = +5 • (-20) + 17 = -3 Subtracting Signed Numbers: When subtracting two numbers, change the sign of the number being subtracted and then follow the rules for adding signed numbers. (Subtracting a number is adding its opposite.) • 8 - (-3) = 8 + (+3) = 11 • -10 - (-8) = -10 + (+8) = -2 • -8 - (+6) = -8 + (-6) = -14 • 13 - 8 = 13 + (-8) = 5 Multiplying or Dividing Signed Numbers: When multiplying or dividing two numbers,      • If the signs are the same, the result is positive.      • If the signs are different, the result is negative. If you have a long series of multiplications of negative values, remove the negative signs in pairs.       (-2)(-3)(-1)(-1)(-5)(-1)(-2) =(2)(3)(1)(1)(5)(1)(-2) = -60 • (+3) x (+9) = +27 • (-6) x (-8) = +48 • (-5) x (+6) = -30 • (+8) x (-2) = -16 • (+12) ÷ (+3) = +4 • (-15) ÷ (-5) = +3 • (-20) ÷ (+2) = -10 • (+18) ÷ (-3) = -6

 Example 1: (-20) + (15) - (13) = ? Answer -18 Example 2: 25 ÷ (-5) = ? Answer -5 Example 3: 8 - (4 - 3) + 6 = ? Answer 13 Example 4: (-6)2 - (-20) + (-4) = ? Answer 52 Example 5: -18 - (-20) + (18) - (20) = ? Answer 0 Example 6: (-24) x (-2) ÷ (-8) = ? Answer -6 Example 7: (-4) x 8 - (-5) + (-7) = ? Answer -34 NOTE: The re-posting of materials (in part or whole) from this site to the Internet is copyright violation and is not considered "fair use" for educators. Please read the "Terms of Use".