What Is an Annex in Math?

Annexing by Addition

• If you start off with the equation:

  2x + 6 = 4y + 16

  You may add a number to either side of the equation. For example, you may add 4 to either side:

  2x + 10 = 4y + 20

  Here annexing simply means adding.

Annexing by Mulitplication

• If you start off with the equation:

  44,670 x 5 = 223,350

  You can multiply either side of they equation by annexing zero:

  446,700 x 5 = 2,233,500

  In this case annexing means multiplication.

Purpose of Annexing by Addition

• Annexing a number to either side of the equation makes it possible to complete the equation. For example:

  2x + 10 = 4y + 20

  Rearranging gives you:

  2x - 4y = 20 -10 = 10

Purpose of Annexing by Multiplication

• If you are asked to make the following calculation:

  44,670 x 5 =

  You may find it easier if you multiply either side of the equation by annexing 0:

  (44,670 x 10) / 2 = 446,700 / 2 = 223,350

  This method is helpful if you find it easier to divide by 2 than to multiply by 5. In many cases this will be true, and annexation can therefore be a useful technique.