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  2. Mental abacus - Wikipedia

    en.wikipedia.org/wiki/Mental_abacus

    The abacus system of mental calculation is a system where users mentally visualize an abacus to carry out arithmetical calculations. [1] No physical abacus is used; only the answers are written down. Calculations can be made at great speed in this way. For example, in the Flash Anzan event at the All Japan Soroban Championship, champion Takeo ...

  3. Trachtenberg system - Wikipedia

    en.wikipedia.org/wiki/Trachtenberg_system

    Trachtenberg system. The Trachtenberg system is a system of rapid mental calculation. The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly. It was developed by the Ukrainian engineer Jakow Trachtenberg in order to keep his mind occupied while being in a Nazi concentration ...

  4. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    3 3 = 27 down 1; 4 3 = 64 down 3; 5 3 = 125 up 1; 6 3 = 216 up 1; 7 3 = 343 down 3; 8 3 = 512 down 1; 9 3 = 729 down 3; 10 3 = 1000 up 1; There are two steps to extracting the cube root from the cube of a two-digit number. For example, extracting the cube root of 29791. Determine the one's place (units) of the two-digit number. Since the cube ...

  5. Chisanbop - Wikipedia

    en.wikipedia.org/wiki/Chisanbop

    Chisanbop or chisenbop (from Korean chi (ji) finger + sanpŏp (sanbeop) calculation [1] 지산법/指算法), sometimes called Fingermath, [2] is a finger counting method used to perform basic mathematical operations. According to The Complete Book of Chisanbop[3] by Hang Young Pai, chisanbop was created in the 1940s in Korea by Sung Jin Pai ...

  6. Zerah Colburn (mental calculator) - Wikipedia

    en.wikipedia.org/wiki/Zerah_Colburn_(mental...

    Zerah was reported to have been able to solve fairly complex problems. For example, the sixth Fermat number is 2 2 5 +1 (or 2 32 +1). The question is whether this number, 4,294,967,297, is prime or not. Zerah calculated in his head that it was not and had a divisor of 641. (Its other proper divisor is 6,700,417).

  7. Abacus - Wikipedia

    en.wikipedia.org/wiki/Abacus

    Abacus-based mental calculation (AMC), which was derived from the abacus, is the act of performing calculations, including addition, subtraction, multiplication, and division, in the mind by manipulating an imagined abacus. It is a high-level cognitive skill that runs calculations with an effective algorithm.