Simply Add app for iPhone and iPad

Simply Add is an app that randomly generates addition problems.
It will generate from 10 to 30 problems.
The problems generated can be as simple as one digit and as complicated as three digits.
To change the number of digits, the number of problems, and wheter to use a timer or not, tap the bottom right icon. Change the picker to your liking then tap the play button located on the bottom left.

When 20 or 30 problems are selected, the app will show a hint when the numbers to be added need to be regrouped for problems between 10 and 20.

The numbers are entered from right to left as you would do a sum on paper.
The green circle identifies the location where the number is expected