Math for Computer Science

6 | Multiplying and dividing negative numbers

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Examples
Practice Problems

Introduction

How are negative numbers multiplied and divided?

Multiplying and dividing negative numbers can be summarized with the following rules:

  • Multiplying a negative and a positive results in a negative
  • Multiplying two negatives results in a positive
  • Dividing a negative and a positive results in a negative
  • Dividing two negatives results in a positive

Examples

Multiplying negative numbers

Q: 3 × (-5)

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A: Multiplying 3 and -5 means adding 3 groups of -5. Since adding negatives results in a move to the left on the number line, 3 × (-5) is -15.


Dividing negative numbers

Q: -15 ÷ (-5)

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A: Dividing -15 and -5 means counting groups of -5 until we get to -15. Since adding negatives results in a move to the left on the number line, our quotient will be positive. Thus, -15 ÷ (-5) = 3.

Practice | Multiplying and Dividing Negative Numbers

Click "Create Report" upon completion of any practice set to document your progress: Example