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  2. Chinese multiplication table - Wikipedia

    en.wikipedia.org/wiki/Chinese_multiplication_table

    The Chinese multiplication table is the first requisite for using the Rod calculus for carrying out multiplication, division, the extraction of square roots, and the solving of equations based on place value decimal notation. It was known in China as early as the Spring and Autumn period, and survived through the age of the abacus; pupils in ...

  3. Product (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Product_(mathematics)

    Product (mathematics) In mathematics, a product is the result of multiplication, or an expression that identifies objects (numbers or variables) to be multiplied, called factors. For example, 21 is the product of 3 and 7 (the result of multiplication), and is the product of and (indicating that the two factors should be multiplied together).

  4. Stepped reckoner - Wikipedia

    en.wikipedia.org/wiki/Stepped_reckoner

    The stepped reckoner or Leibniz calculator was a mechanical calculator invented by the German mathematician Gottfried Wilhelm Leibniz (started in 1673, when he presented a wooden model to the Royal Society of London [2] and completed in 1694). [1] The name comes from the translation of the German term for its operating mechanism, Staffelwalze ...

  5. Napier's bones - Wikipedia

    en.wikipedia.org/wiki/Napier's_bones

    Napier gave details of a scheme for arranging the tables so that no rod has two copies of the same table, enabling every possible four-digit number to be represented by 4 of the 10 rods. A set of 20 rods, consisting of two identical copies of Napier's 10 rods, allows calculation with numbers of up to eight digits, and a set of 30 rods can be ...

  6. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    Second example: 87 x 11 = 957 because 8 + 7 = 15 so the 5 goes in between the 8 and the 7 and the 1 is carried to the 8. So it is basically 857 + 100 = 957. Or if 43 x 11 is equal to first 4+3=7 (For the tens digit) Then 4 is for the hundreds and 3 is for the tens.

  7. Pascal's calculator - Wikipedia

    en.wikipedia.org/wiki/Pascal's_calculator

    Pascal's calculator (also known as the arithmetic machine or Pascaline) is a mechanical calculator invented by Blaise Pascal in 1642. Pascal was led to develop a calculator by the laborious arithmetical calculations required by his father's work as the supervisor of taxes in Rouen. [2] He designed the machine to add and subtract two numbers ...

  8. Multiplication table - Wikipedia

    en.wikipedia.org/wiki/Multiplication_table

    Multiplication table. In mathematics, a multiplication table (sometimes, less formally, a times table) is a mathematical table used to define a multiplication operation for an algebraic system. The decimal multiplication table was traditionally taught as an essential part of elementary arithmetic around the world, as it lays the foundation for ...

  9. Air changes per hour - Wikipedia

    en.wikipedia.org/wiki/Air_changes_per_hour

    Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each ...