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  2. Slide rule - Wikipedia

    en.wikipedia.org/wiki/Slide_rule

    The pocket-sized Hewlett-Packard HP-35 scientific calculator was the first handheld device of its type, but it cost US$395 in 1972. This was justifiable for some engineering professionals, but too expensive for most students. Around 1974, lower-cost handheld electronic scientific calculators started to make slide rules largely obsolete.

  3. Order of operations - Wikipedia

    en.wikipedia.org/wiki/Order_of_operations

    Calculators generally perform operations with the same precedence from left to right, [1] but some programming languages and calculators adopt different conventions. For example, multiplication is granted a higher precedence than addition, and it has been this way since the introduction of modern algebraic notation.

  4. Casting out nines - Wikipedia

    en.wikipedia.org/wiki/Casting_out_nines

    The digital root of the result of this calculation is then compared with that of the result of the original calculation. If no mistake has been made in the calculations, these two digital roots must be the same. Examples in which casting-out-nines has been used to check addition, subtraction, multiplication, and division are given below.

  5. Chisanbop - Wikipedia

    en.wikipedia.org/wiki/Chisanbop

    The Chisanbop system. When a finger is touching the table, it contributes its corresponding number to a total. 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.

  6. Napier's bones - Wikipedia

    en.wikipedia.org/wiki/Napier's_bones

    Using the multiplication tables embedded in the rods, multiplication can be reduced to addition operations and division to subtractions. Advanced use of the rods can extract square roots. Napier's bones are not the same as logarithms, with which Napier's name is also associated, but are based on dissected multiplication tables.

  7. Slide calculator - Wikipedia

    en.wikipedia.org/wiki/Slide_calculator

    A slide calculator, also known as an Addiator after the best-known brand, is a mechanical calculator capable of addition and subtraction, once made by Addiator Gesellschaft of Berlin, Germany. Variants of it were manufactured from 1920 until 1982. The devices were made obsolete by the electronic calculator.

  8. Scientific calculator - Wikipedia

    en.wikipedia.org/wiki/Scientific_calculator

    Casio fx-77, a solar-powered digital calculator from the 1980s using a single-line LCD. 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.

  9. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    492 is close to 500, which is easy to multiply by. Add and subtract 8 (the difference between 500 and 492) to get 492 -> 484, 500. Multiply these numbers together to get 242,000 (This can be done efficiently by dividing 484 by 2 = 242 and multiplying by 1000). Finally, add the difference (8) squared (8 2 = 64) to the result: 492 2 = 242,064