 Adding Signed Numbers: |
Examples: |
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 |
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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 |
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The slang "naked" number is the number without its sign. A naked -8 would be 8 (or the absolute value of -8).
Subtracting Signed Numbers: |
Examples: |
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 |
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Multiplying or Dividing Signed Numbers: |
Examples: |
| When multiplying 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 |
When dividing two numbers,
• If the signs are the same, the result is positive.
• If the signs are different, the result is negative.
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• (-16) ÷ (+8) = -2
• (-24) ÷ (-6) = +4
• (+3) ÷ (-4) = -0.75 or -¾
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For help with signed numbers
(negation vs subtraction)
on your calculator,
click here. |
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Give it a try!
Example 1: (20) + (-15) = ? |
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Example 2: 25 ÷ (-5) = ? |
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Example 3: 8 - (-3) = ? |
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Example 4: (-20) + (-4) = ? |
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Example 5: -18 - (-20) = ? |
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Example 6: (-24) x (-2) = ? |
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Example 7: (-4) x (5) = ? |
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