This neat little app will work on PCs and MACs as well as Linux machines. You don't need an administrator's password to install it either. Just save to the location of your choice, unzip and you are ready to go.
In order for it to work you must have a current java installed (free). If you don't have it follow the link:
For PC: http://java.com/en/download/help/windows_manual_download.xml
For MAC: http://kb2.adobe.com/cps/909/cpsid_90908.html
The software is a simple java application that asks for the 6th number in a series of numbers that follow a skip counting pattern. The first three numbers are given, 4th and 5th are blank, the 6th is the one the user enters. It randomly uses skip counting by 2, 3, 4, 5, and 10. It keeps a score of correct answers. Finally as the user answers correctly the first number gets increasingly larger, when answered incorrectly the initial number goes one step back, therefore not getting beyond their capability.
By purchasing this software you may install it in as many computers as you may use in your classroom and/or your house. It is a simple application written on java, it will work on a mac, pc, or even a linux as long as they have a current java environment installed (free to install).