In the Opposite-Change Addition app the user can keep adding a number to one addend and subtract the same number from the other addend until the addition problem can be solved easily. The opposite-change rules states that if you subtract a number from one addend and add the same number to the other addend, the sum remains the same. An addition problem 267 + 289 is easier to solve when it has been changed into 256 + 300. Features: - The numbers can have up to 3 digits - You can set your own problems Other iDevBooks math apps iDevBooks math apps have been reviewed and endorsed by Wired.com, Common Sense Media, and other respected sites and organizations. Feedback and requests for new features New ideas to make this app better are welcome. Please visit idevbooks.com to give feedback. Privacy This app has no ads or in-app purchases and it does not transmit any data during the operation of the app. This app also does not contain any links to other apps or the web.