Subtraction software that has more than 400 possible questions. Starting at beginner level for those starting out moving to an advanced level as you progress. Included is a speed test level that gives you the chance to see how many you can get right in 100 seconds. This software has been designed to give people of all ages the opportunity to practice at home what they learn in school. The user has the choice of taking a 20 or 40 question test for 9 of the levels. 2 of the levels are extremely hard and don’t offer this feature. The starter levels give the user the opportunity to turn the timer off. Having a timer that can be turned off helps those that are starting out.