# What Is an Annex in Math?

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Annexes in math may sound complex but they are in fact very simple. However, the word "annex" has multiple meanings, which can make it confusing. Annexing a number to either side of an equation may involve either adding or multiplying. Annexing may be useful when attempting to solve algebra.

## 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.

## References

• "Complete Mathematics"; T. Johnson et al.; 2010
• Photo Credit Hemera Technologies/AbleStock.com/Getty Images
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