bullet 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
   
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
plainAS
The slang "naked" number is the number without its sign. A naked -8 would be 8 (or the absolute value of -8).


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bullet 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
plainSub


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bullet 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
plainMD


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ti84c
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) - (13) = ?  


 
Example 2: 25 ÷ (-5) = ? 


 
Example 3: 8 - (4 - 3) + 6 = ?


 
Example 4: (-6)2 - (-20) + (-4) = ?


 
Example 5: -18 - (-20) + (18) - (20) = ?


 
Example 6: (-24) x (-2) ÷ (-8) = ?


 
Example 7: (-4) x 8 - (-5) + (-7) = ?

 

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