Dividing Rational Numbers

Student Summary

Any division problem is actually a multiplication problem:

  • 6÷2=36 \div 2 = 3 because 23=62 \boldcdot 3 = 6.
  • 6÷-2=-36 \div \text- 2 = \text-3 because -2-3=6\text-2 \boldcdot \text-3 = 6.
  • -6÷2=-3\text-6 \div 2 = \text-3 because 2-3=-62 \boldcdot \text-3 = \text-6.
  • -6÷-2=3\text-6 \div \text-2 = 3 because -23=-6\text-2 \boldcdot 3 = \text-6.

Because we know how to multiply signed numbers, that means we know how to divide them.

  • A positive number divided by a negative number always results in a negative number.
  • A negative number divided by a positive number always results in a negative number.
  • A negative number divided by a negative number always results in a positive number.

A number that can be used in place of the variable that makes the equation true is called a solution to the equation. For example, for the equation x÷-2=5x \div \text-2 = 5, the solution is -10 because it is true that -10÷-2=5\text-10 \div \text-2 = 5.

Visual / Anchor Chart

Standards

Building On
7.NS.2

Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.

Addressing
7.NS.2.b

Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.

Building Toward
7.EE.4.a

Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.