Adding and Subtracting Integers or Whole Numbers

- - Pre-Algebra

Adding and Subtracting Integers or Whole Numbers HeaderAdding and subtracting integers or whole numbers need the understanding of positive and negative integers. From your previous experience in arithmetic you are aware of the necessity for a system of numbers which will denote direction as well as amount. Thus, if +3 indicates 3 units to the right on a number scale, -3 indicates 3 units to the left.

Numbers that tell us which way as well as how much or how many are called signed numbers.

A signed number preceded by a plus (+) sign is called a positive number; if it is preceded by a minus (-) sign, it is called a negative number. If no sign is expressed, the number is considered to be positive.

The value of a number without regard to its sign is called its absolute value.

Rules of Adding and Subtracting Whole Numbers or Integers
Addition:

  • To add two numbers having like signs, find the sum of their absolute values and prefix the common sign. 
  • To add two numbers having unlike signs, find the difference of their absolute values and prefix the sign of the greater number.
Subtraction:
  • Mentally change the sign of the subtrahend and proceed as in arithmetic addition.
Examples: Find each sum.
  1. (-10) + 6 = -4   
  2. (-9) + (-5) = -14
  3. (-3) + 15 = 12  
  4. 10 + 5 = 15
  5. 2 +12 = 14
Examples: Find each difference. 
  1. 3 − (-4) = 3 + 4 = 7 
  2. (-3) − 20 = (-3) + (-20) = -23
  3. 9 − 4 = 5 
  4. (-7) − (-6) = (-7) + 6 = -1
  5. 10 − 2 = 8
Examples: Evaluate each expression.
  1. (-20) − 24 = (-20) + (-24) = -44 
  2. (-10) + (-20) = -30
  3. 3 + 5 + 14 = 22  
  4. 26 + (-10) + 5 = 21
  5. 1 − (-10) − 8 = 1 + 10 − 8 =  3

Adding and Subtracting Integers or Whole Numbers Worksheets

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