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  2. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    The products of small numbers may be calculated by using the squares of integers; for example, to calculate 13 × 17, one can remark 15 is the mean of the two factors, and think of it as (15 − 2) × (15 + 2), i.e. 15 2 − 2 2. Knowing that 15 2 is 225 and 2 2 is 4, simple subtraction shows that 225 − 4 = 221, which is the desired product.

  3. Order of operations - Wikipedia

    en.wikipedia.org/wiki/Order_of_operations

    For example, multiplication is granted a higher precedence than addition, and it has been this way since the introduction of modern algebraic notation. [2] [3] Thus, in the expression 1 + 2 × 3, the multiplication is performed before addition, and the expression has the value 1 + (2 × 3) = 7, and not (1 + 2) × 3 = 9.

  4. Multiplication - Wikipedia

    en.wikipedia.org/wiki/Multiplication

    Multiplication can also be thought of as scaling. Here, 2 is being multiplied by 3 using scaling, giving 6 as a result. Animation for the multiplication 2 × 3 = 6 4 × 5 = 20. The large rectangle is made up of 20 squares, each 1 unit by 1 unit. Area of a cloth 4.5m × 2.5m = 11.25m 2; 4 ⁠ 1 / 2 ⁠ × 2 ⁠ 1 / 2 ⁠ = 11 ⁠ 1 / 4 ⁠

  5. Pinwheel calculator - Wikipedia

    en.wikipedia.org/wiki/Pinwheel_calculator

    A pinwheel calculator is a class of mechanical calculator described as early as 1685, and popular in the 19th and 20th century, calculating via wheels whose number of teeth were adjustable. These wheels, also called pinwheels, could be set by using a side lever which could expose anywhere from 0 to 9 teeth, and therefore when coupled to a ...

  6. Calculator - Wikipedia

    en.wikipedia.org/wiki/Calculator

    The interior of a Casio fx-20 scientific calculator from the mid-1970s, using a VFD. The processor integrated circuit (IC) is made by NEC (marked μPD978C). Discrete electronic components like capacitors and resistors and the IC are mounted on a printed circuit board (PCB). This calculator uses a battery pack as a power source.

  7. Multiplication sign - Wikipedia

    en.wikipedia.org/wiki/Multiplication_sign

    The multiplication sign (×), also known as the times sign or the dimension sign, is a mathematical symbol used to denote the operation of multiplication, which results in a product. [ 1 ] The symbol is also used in botany , in botanical hybrid names .

  8. Elementary arithmetic - Wikipedia

    en.wikipedia.org/wiki/Elementary_arithmetic

    Multiplication is a mathematical operation of repeated addition. When two numbers are multiplied, the resulting value is a product. The numbers being multiplied are multiplicands, multipliers, or factors. Multiplication can be expressed as "five times three equals fifteen," "five times three is fifteen," or "fifteen is the product of five and ...

  9. Napier's bones - Wikipedia

    en.wikipedia.org/wiki/Napier's_bones

    Napier's bones is a manually operated calculating device created by John Napier of Merchiston, Scotland for the calculation of products and quotients of numbers. The method was based on lattice multiplication, and also called rabdology, a word invented by Napier.