Signed Numbers

Multiplying and Dividing Signed Numbers

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Multiplying and Dividing Signed Numbers

Rules for Multiplying/Dividing:

Multiplying

  1. The product of two numbers with the same signs is positive.
  2. The product of two numbers with different signs is negative.
    Examples:
    (+2) x (+9) = +18
    (-7) x (-8) = +56
    (-5) x (+4) = -20
    (+7) x (-2) = -14
  3. 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

Dividing

  1. The quotient of two numbers with the same sign is positive.
  2. The quotient of two numbers with different signs is negative.

Multiplying and Dividing Signed Numbers 1

Subtracting Signed Numbers

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Subtracting Signed Numbers

Rule for Subtracting:
You can subtract a number by adding its opposite.

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.)
Examples:

  • 7 – (-3) = 7 + (+3) = 10
  • -10 – (-7) = -10 + (+7) = -3
  • -8 – (+6) = -8 + (-6) = -14
  • 13 – 4 = 13 + (-4) = 9

Adding Signed Numbers 1

Adding Signed Numbers

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Adding Signed Numbers

Rules for Adding:

  1. When you add two numbers with the same signs,
    1. add the absolute values, and
    2. write the sum (the answer) with the sign of the numbers.
      Examples:
      (+5) + (+7) = +12
      (-6) + (-8) = -14
      (9) + (5) = 14
  2. When you add 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.
      Examples:
      (+7) + (-9) = -2
      (-12) + (+15) = +3
      (-20) + 14 = -6

Adding Signed Numbers 1