App: Trade-First Subtraction
Developer: Esa Helttula
Genres: Education

This app can be used to teach and study the trade-first subtraction method. The app is easy to use and it has an intuitive interactive interface with customizable colors and other settings. The user can solve random subtraction problems with small and large numbers. The number of digits in the numbers can be set. 

Endorsed by Teachers 

Rita Zeni, Ecole Sandy Hill Elementary, Abbotsford, BC, Canada: 

"The math apps by Esa Helttula allow students to practice and reinforce the specific computation strategies taught in class, with as much or as little scaffolding as necessary. 
They also provide individualized feedback to each student, with an immediacy that is not always possible through pencil and paper practice. Being able to adjust the level of difficulty to suit their needs is also very motivating for the students. I am so glad to have come across this great educational tool!" 

The Trade-First Method 

The trade-first subtraction method is similar to the traditional column subtraction method. The method has two stages. All of the "trading" or "borrowing" is done first. Then the subtractions are solved. This gives the method it's name, "trade-first." 

In the Everyday Mathematics curriculum the trade-first method is the focus algorithm for subtraction. 

The App is Easy to Use 

The numbers are aligned automatically so that you can concentrate on solving the operations for each column. 

Borrowing is animated step by step so you can see what happens. Borrowing over several columns is also supported. 

After you solve the operation for each column the correct answer will fly to the right place. If the user presses the wrong button the answer will appear above the keyboard but it will not move. 

Features: 

- Each number can have from 2 to 5 digits 
- Problems can be custom or random
- 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 
- The lines separating the columns can be hidden 

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 for iOS and Mac are Column Addition, Long Multiplication, Long Division, Column Subtraction, Visual Multiplication Table, Partial Differences Subtraction, Partial Products Multiplication, 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. 

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.

Release notes: