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  2. 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 ...

  3. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    Since 9 = 10 − 1, to multiply a number by nine, multiply it by 10 and then subtract the original number from the result. For example, 9 × 27 = 270 − 27 = 243. This method can be adjusted to multiply by eight instead of nine, by doubling the number being subtracted; 8 × 27 = 270 − (2×27) = 270 − 54 = 216.

  4. Casting out nines - Wikipedia

    en.wikipedia.org/wiki/Casting_out_nines

    Casting out nines. Arithmetic procedure of verifying operations using modulo characteristics of digit 9. Casting out nines is any of three arithmetical procedures: [1] Adding the decimal digits of a positive whole number, while optionally ignoring any 9s or digits which sum to 9 or a multiple of 9. The result of this procedure is a number which ...

  5. Multiplication algorithm - Wikipedia

    en.wikipedia.org/wiki/Multiplication_algorithm

    A multiplication algorithm is an algorithm (or method) to multiply two numbers. Depending on the size of the numbers, different algorithms are more efficient than others. Numerous algorithms are known and there has been much research into the topic. The oldest and simplest method, known since antiquity as long multiplication or grade-school ...

  6. Karatsuba algorithm - Wikipedia

    en.wikipedia.org/wiki/Karatsuba_algorithm

    The Karatsuba algorithm is a fast multiplication algorithm. It was discovered by Anatoly Karatsuba in 1960 and published in 1962. [1][2][3] It is a divide-and-conquer algorithm that reduces the multiplication of two n -digit numbers to three multiplications of n /2-digit numbers and, by repeating this reduction, to at most single-digit ...

  7. Chisanbop - Wikipedia

    en.wikipedia.org/wiki/Chisanbop

    With the chisanbop method it is possible to represent all numbers from 0 to 99 with the hands, rather than the usual 0 to 10, and to perform the addition, subtraction, multiplication and division of numbers. [4] The system has been described as being easier to use than a physical abacus for students with visual impairments. [5]

  8. Montgomery modular multiplication - Wikipedia

    en.wikipedia.org/wiki/Montgomery_modular...

    Montgomery modular multiplication relies on a special representation of numbers called Montgomery form. The algorithm uses the Montgomery forms of a and b to efficiently compute the Montgomery form of ab mod N. The efficiency comes from avoiding expensive division operations. Classical modular multiplication reduces the double-width product ab ...

  9. Schönhage–Strassen algorithm - Wikipedia

    en.wikipedia.org/wiki/Schönhage–Strassen...

    Schönhage (on the right) and Strassen (on the left) playing chess in Oberwolfach, 1979. The Schönhage–Strassen algorithm is an asymptotically fast multiplication algorithm for large integers, published by Arnold Schönhage and Volker Strassen in 1971. [1] It works by recursively applying fast Fourier transform (FFT) over the integers modulo .

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