Using an Abacus
Date: 1/12/96 at 15:22:27 From: Anonymous Subject: Abacus Our fifth grade class of gifted and talented math students is trying to figure out how to use an abacus. Please send any information you have. Thank you. Andy, Alex, David, and Bret
Date: 1/12/96 at 17:23:48 From: Doctor Sarah Subject: Re: Abacus Hi there! I'm going to hope that since you're sending your question via the Internet, you have access to a Web browser like Netscape, since the best way to answer your question may be to send you to http://www.ee.ryerson.ca:8080/~elf/abacus/ This is a great site with an interactive abacus, an Introduction, and detailed instructions for adding and subtracting. Here are a few excerpts: 2.0 Addition Addition on the abacus involves registering the numbers on the beads in the straight-forward left-to-right sequence they are written down in. As long as the digits are placed correctly, and the carry's noted properly, the answer to the operation immediately presents itself right on the abacus. There are 4 approaches to performing additions (or subtractions), each applied to particular situations. Each of thesetechniques is explained (!) in tabular form in the sections that follow. 2.1 Simple Addition When performing the addition 6+2, one would move 1 bead from the upper deckdown (value = 5) and one bead from the lower deck up (value = 1); this represents 6. Moving 2 beads from the lower deck (in the same column) up (value = 1 * 2 beads = 2) would complete the operation. The answer is then obtained by reading resultant bead positions. . . . 3.0 Subtraction Subtraction is performed by first registering the minuend and then subtracting, starting from the left, by removing beads form either or both the lower or upper decks. The final bead-positions represent the answer. 3.1 Simple Taking-off This is achieved by simply taking off one or more beads from the lower deck, or sometimes both. Example: When subtracting 7 (represented by -5-2 = -7) from 9, remove 1 bead from the upper- deck (-5) and 2 beads from the lower deck (-2). The remaining 2 beads represent the result. 3.2 Combined Adding-up And Taking Off When the number of beads in the lower deck is less than the subtracter (the number being subtracted), one or more beads are added in the lower deck and 1 bead is removed from the upper-deck. Example: When subtracting 4 (+1-5 = -4) from 7 (represented by 1 bead in the upper-deck and 2 beads in the lower deck (less than 4, the subtracter), one bead is added to the lower deck (+1) and 1 bead is removed from the upper-deck (-5) leaving 3 beads, representing the result. _________________________________ I hope you have an abacus to practice with! - Doctor Sarah, The Math Forum
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