Inverse relationship of Addition and Subtraction

There is an inverse relationship between addition and subtraction.

If a math fact is considered, for example 3 + 7 = 10. Then the following are also true:

  • 10 - 3 = 7
  • 10 - 7 = 3

Similar relationships exist for subtraction, for example 10 - 3 = 7. Then the following are also true:

  • 3 + 7 = 10
  • 7 + 3 = 10

The reason for this is that we are dealing with an equation. An equation is balanced or the same on either side of the equals (=) sign. If exactly the same thing is done to both sides of the equation, it will still be balanced or equal.

In the example above we start with the equation 3 + 7 = 10

  • Subtract the same number from both sides 3 + 7 - 3 = 10 - 3
  • On the left side the 3 and -3 produce 0 which leaves 7 = 10 - 3
  • Turning the equation around to be in more normal form 10 - 3 = 7


What number should replace the question marks?

 

Notice: AAAMath licensed software. This file and associated files are copyrighted software that is protected under United States and international copyright laws and agreements. It is a violation of the law to distribute or duplicate this software. This includes distribution outside of the specific physical household, classroom, or school location for which the license was purchased. Violators will be prosecuted to the full extent of the law. If you notice a violation please contact AAAMath at copyright@aaamath.com

Copyright (C) 2004 J. Banfill. All Rights Reserved.