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.
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• (+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.
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• (+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.)
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• 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
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• (+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
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