Changes

[http://en.wikipedia.org/wiki/Abacus Abacus] lets the learner explore different representations of numbers using different mechanical counting systems developed by the ancient Romans and Chinese. There are several different variants available for exploration: a [http://en.wikipedia.org/wiki/Suanpan suanpan], the traditional Chinese abacus with 2 beads on top and 5 beads below; a [http://en.wikipedia.org/wiki/Soroban soroban], the traditional Japanese abacus with 1 bead on top and 4 beads below; the [http://en.wikipedia.org/wiki/Abacus#Russian_abacus schety], the traditional Russian abacus, with 10 beads per column, with the exception of one column with just 4 beads used for counting in fourths; and the [http://en.wikipedia.org/wiki/Abacus#Native_American_abaci nepohualtzintzin], a Mayan abacus, 3 beads on top and 4 beads below (base 20). There is also a binary abacus, a hexadecimal abacus, and an abacus that lets you calculate with common fractions: 1/2, 1/3, 1/4, 1/5, 1/6, 1/8, 1/9, 1/10, and 1/12. As of Version 9, there is a customization toolbar that lets you design your own abacus.

[http://en.wikipedia.org/wiki/Abacus Abacus] lets the learner explore different representations of numbers using different mechanical counting systems developed by the ancient Romans and Chinese. There are several different variants available for exploration: a [http://en.wikipedia.org/wiki/Suanpan suanpan], the traditional Chinese abacus with 2 beads on top and 5 beads below; a [http://en.wikipedia.org/wiki/Soroban soroban], the traditional Japanese abacus with 1 bead on top and 4 beads below; the [http://en.wikipedia.org/wiki/Abacus#Russian_abacus schety], the traditional Russian abacus, with 10 beads per column, with the exception of one column with just 4 beads used for counting in fourths; and the [http://en.wikipedia.org/wiki/Abacus#Native_American_abaci nepohualtzintzin], a Mayan abacus, 3 beads on top and 4 beads below (base 20). There is also a binary abacus, a hexadecimal abacus, and several abacuses that lets you calculate with common fractions: 1/2, 1/3, 1/4, 1/5, 1/6, 1/8, 1/9, 1/10, and 1/12. As of Version 9, there is a customization toolbar that lets you design your own abacus.

<gallery>

<gallery>

File:Hexadecimal.png|hexadecimal (base 16)

File:Hexadecimal.png|hexadecimal (base 16)

File:Fraction.png|fractions (1/2, 1/3, 1/4,...)

File:Fraction.png|fractions (1/2, 1/3, 1/4,...)

File:Custom-abacus.png|custom, as shown: octal (base 8)

File:Custom-abacus.png|custom, as shown: octal (base 8)

</gallery>

</gallery>