Refresher Topic
bullet 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
bullet Subtracting Signed 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

bullet Multiplying or Dividing Signed 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

 

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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