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  2. Extraneous and missing solutions - Wikipedia

    en.wikipedia.org/wiki/Extraneous_and_missing...

    In mathematics, an extraneous solution (or spurious solution) is one which emerges from the process of solving a problem but is not a valid solution to it. [1] A missing solution is a valid one which is lost during the solution process.

  3. 24 (puzzle) - Wikipedia

    en.wikipedia.org/wiki/24_(puzzle)

    The original version of 24 is played with an ordinary deck of playing cards with all the face cards removed. The aces are taken to have the value 1 and the basic game proceeds by having 4 cards dealt and the first player that can achieve the number 24 exactly using only allowed operations (addition, subtraction, multiplication, division, and parentheses) wins the hand.

  4. Pascaline - Wikipedia

    en.wikipedia.org/wiki/Pascaline

    He designed the machine to add and subtract two numbers directly and to perform multiplication and division through repeated addition or subtraction. Pascal's calculator was especially successful in the design of its carry mechanism, which adds 1 to 9 on one dial, and carries 1 to the next dial when the first dial changes from 9 to 0. His ...

  5. 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.

  6. Mechanical calculator - Wikipedia

    en.wikipedia.org/wiki/Mechanical_calculator

    Friden made a calculator that also provided square roots, basically by doing division, but with added mechanism that automatically incremented the number in the keyboard in a systematic fashion. The last of the mechanical calculators were likely to have short-cut multiplication, and some ten-key, serial-entry types had decimal-point keys.

  7. Scientific calculator - Wikipedia

    en.wikipedia.org/wiki/Scientific_calculator

    A scientific calculator is an electronic calculator, either desktop or handheld, designed to perform calculations using basic (addition, subtraction, multiplication, division) and advanced (trigonometric, hyperbolic, etc.) mathematical operations and functions.

  8. Calculator input methods - Wikipedia

    en.wikipedia.org/wiki/Calculator_input_methods

    The simplest example given by Thimbleby of a possible problem when using an immediate-execution calculator is 4 × (−5). As a written formula the value of this is −20 because the minus sign is intended to indicate a negative number, rather than a subtraction, and this is the way that it would be interpreted by a formula calculator.

  9. Mixed numbers - Wikipedia

    en.wikipedia.org/?title=Mixed_numbers&redirect=no

    This page was last edited on 23 June 2020, at 13:37 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...