Rules for Calculating Positive and Negative Numbers

  • When you add a positive and a positive number, the answer is positive: i.e. 3 + 2 = 5
  • When you add a positive and a negative number, you have to subtract the smaller number from the larger, and place the sign of the larger number in front of the answer: i.e. -3 + 2 = -1, and 3 + (-2) = 1
  • When you add two negative numbers, you have to add the numbers, and place a negative sign in front of the answer:
    i.e. (-3) + (-2) = -5
  • When you are subtracting two negative numbers, you have to add the opposite of the second number and re-write the problem before solving it: i.e. (-3) - (-2) = (-3) + 2 = -1
  • When you are multiplying or dividing positive numbers, the answer will be positive: i.e. 2 x 3 = 6 and 10 ÷ 2 = 5
  • When multiplying or dividing a positive and a negative number, the answer will be negative: i.e. (-2) x 3 = -6, (-10) ÷2 = -5, 2 x (-3) = -6 and 10 ÷ (-2) = -5
  • When multiplying or dividing two negative numbers, the answer will be positive: i.e. (-2) x (-3) = 6 and (-10) ÷(-5) = 2

(Submitted by: Cathy Pasinski; Last updated: September 12, 2009)

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