This math app can be used to teach and study the equal addition subtraction method. The user can solve random or custom subtraction problems with small and large numbers. The number of digits in the numbers can be set.
The equal addition subtraction method is also called the ‘borrow and repay’ method or equal additions method for subtraction. Today the method is used in Australia and Latin America. The equal addition used to be a very popular method for subtraction in US until the middle of 20th century.
The equal addition subtraction method
The method is based upon the idea that adding the same amount to two numbers will not affect the difference between the two numbers. The process can be thought as:
- Work column by column from right to left
- When the digit of the first number is smaller than the corresponding digit of the second number, add ten to the digit of the first number and one to the digit of the second number in the next column to the left.
Review by professor Tim Pelton
Tim Pelton, assistant professor of Mathematics Education at the University of Victoria, reviewed the Column Subtraction app (that is very similar to this app) and wrote:
“With the ‘show current operation’ option turned on, they are constantly reminded of the next step, which can lead to efficient practice of the procedure. Then by turning off the current operation your child is able to practice remembering the steps on his/her own. Because no wrong entries are allowed the app provides a passive form of positive reinforcement and your child will likely improve in both confidence and competence with respect to the procedure.”
Easy to use
The numbers are aligned automatically so that you can concentrate on solving the operations for each column. After you solve the operation for each column the correct answer will fly to the right place. If you tap the wrong button the answer will appear above the keyboard but it will not move.
- Each number can have up to 5 digits
- Problems can be random or custom
- The current operation for each column can be hidden
- The operands of the current operation can be highlighted
- Colors of the interface can be changed
- The speed of the animations can be set
- Different interface on iPhone and iPad
Other iDevBooks math apps
iDevBooks math apps have been reviewed and endorsed by Wired.com, IEAR.org, Edudemic.com, Teachers with Apps, and other respected sites and organizations.
Some of the other 40 iDevBooks math apps are Column Subtraction, Column Addition, Long Division, Lattice Multiplication, Visual Multiplication Table, Fraction Math, Partial Differences Subtraction, Partial Quotients Division, Partial Sums Addition, Decimal Rounding, etc.
Feedback and requests for new features
New ideas to make this app better are welcome. Please visit idevbooks.com to give feedback.
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.
- support for iOS 13
- new interface with support for latest iPad and iPhone models
- new theme colors
Ratings and Reviews
With Family Sharing set up, up to six family members can use this app.