Abacus for Kids

The abacus, also called a counting frame, is a calculating tool used primarily in parts of Asia for performing arithmetic processes. The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks in Asia, Africa, and elsewhere. Around the world, abaci have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic.
The Chinese abacus, known as the suànpán (算盤, lit. "Counting tray"), usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom for both decimal and hexadecimal computation. Each bead in the upper deck has a value of 5; each bead in the lower deck has a value of 1. Beads are considered counted, when moved towards the beam that separates the two decks. When 5 beads are counted in the lower deck, the result is "carried" to the upper deck; after both beads in the upper deck are counted, the result (10) is then carried to the left-most adjacent column. The right-most column is the ones column; the next adjacent to the left is the tens column; the next adjacent to the left is the hundreds column, and so on.

This application includes:
1. the Basic Training
1.1. Addition and subtraction of the const 37: add 37 for 3 times to get 111, and another 3 times to get 222, and so on. When the data is 999, continue to subtract 37 from it until it reaches 0.
1.2. Addition and subtraction of the const 185: add 185 for 6 times to get 1110, and another 6 times to get 2220, and so on. When the data is 9990, continue to subtract 185 from it until it reaches 0.
1.3. Addition and subtraction of the const 625: add 625 for 16 times to get 10000, and another 16 times to get 20000, and so on. When the data is 62500, continue to subtract 625 from it until it reaches 0.
1.4. Addition and subtraction of the const 16835: add 16835 for 3 times to get 50505, and another 3 times to get 101010, and so on. When the data is 1010100, continue to subtract 16835 from it until it reaches 0.
1.5. There're other consts such as 16875 and 123456789.
1.6. 100: add 1, 2, 3, …, 99 and 100 to get 5050 and then subtract 1, 2, 3, …, 99 and 100 to get 0.

2. Abacus formulas
The application will show abacus formulas to help the user after the user has beaded in the first number. The right-bottom can be pressed to toggle the hint. Abacus formulas include the Addition Tables and the Subtraction Tables can be referenced at: http://www.tux.org/~bagleyd/AbacusLee.html

3. Abacus Tests
The user can select Easy or Difficult tests. In the Easy mode, there are 2 or 3 digits in each number, and 4 or 5 in Difficult mode. When the user reaches the right answer, the next question will be automatically displayed.