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長榮訂位代號查詢網站相關資料
Digital Abacus
Indian Abacus Mental Arithmetic Education for Brain skills:The Abacus over the last 2000 years had evolved to the modern but still a manual version po …
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Napier's abacus
This abacus was created by John Napier of Merchiston in 1617 for calculation of products and quotients of numbers. The method was based on Arab mathem …
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