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  2. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    result: 49; Similarly add 7 + 5 = 12, then add the carried 1 to get 13. Place 3 to the result and carry the 1. result: 349; Add the carried 1 to the highest valued digit in the multiplier, 7 + 1 = 8, and copy to the result to finish. Final product of 759 × 11: 8349; Further examples: −54 × −11 = 5 5+4(9) 4 = 594

  3. Methods of computing square roots - Wikipedia

    en.wikipedia.org/wiki/Methods_of_computing...

    A method analogous to piece-wise linear approximation but using only arithmetic instead of algebraic equations, uses the multiplication tables in reverse: the square root of a number between 1 and 100 is between 1 and 10, so if we know 25 is a perfect square (5 × 5), and 36 is a perfect square (6 × 6), then the square root of a number greater than or equal to 25 but less than 36, begins with ...

  4. Circle packing in a square - Wikipedia

    en.wikipedia.org/wiki/Circle_packing_in_a_square

    Solutions (not necessarily optimal) have been computed for every N ≤ 10,000. [2] Solutions up to N = 20 are shown below. [2] The obvious square packing is optimal for 1, 4, 9, 16, 25, and 36 circles (the six smallest square numbers), but ceases to be optimal for larger squares from 49 onwards.

  5. Fraction - Wikipedia

    en.wikipedia.org/wiki/Fraction

    Percentages greater than 100 or less than zero are treated in the same way, e.g. 311% means 311 ⁄ 100 and −27% means −27 ⁄ 100. The related concept of permille , or parts per thousand (ppt), means a denominator of 1000, and this parts-per notation is commonly used with larger denominators, such as million and billion , e.g. 75 parts per ...

  6. Approximations of π - Wikipedia

    en.wikipedia.org/wiki/Approximations_of_π

    At about the same time, the Egyptian Rhind Mathematical Papyrus (dated to the Second Intermediate Period, c. 1600 BCE, although stated to be a copy of an older, Middle Kingdom text) implies an approximation of π as 256 ⁄ 81 ≈ 3.16 (accurate to 0.6 percent) by calculating the area of a circle via approximation with the octagon. [5] [12]

  7. 1/4 + 1/16 + 1/64 + 1/256 + ⋯ - ⋯ - Wikipedia

    en.wikipedia.org/wiki/1/4_%2B_1/16_%2B_1/64_%2B...

    Today, a more standard phrasing of Archimedes' proposition is that the partial sums of the series 1 + ⁠ 1 / 4 ⁠ + ⁠ 1 / 16 ⁠ + ⋯ are: + + + + = +. This form can be proved by multiplying both sides by 1 − ⁠ 1 / 4 ⁠ and observing that all but the first and the last of the terms on the left-hand side of the equation cancel in pairs.

  8. Scientific notation - Wikipedia

    en.wikipedia.org/wiki/Scientific_notation

    A Texas Instruments TI-84 Plus calculator display showing the Avogadro constant to three significant figures in E notation. The first pocket calculators supporting scientific notation appeared in 1972. [14] To enter numbers in scientific notation calculators include a button labeled "EXP" or "×10 x", among other variants.

  9. Formula for primes - Wikipedia

    en.wikipedia.org/wiki/Formula_for_primes

    Because the set of primes is a computably enumerable set, by Matiyasevich's theorem, it can be obtained from a system of Diophantine equations. Jones et al. (1976) found an explicit set of 14 Diophantine equations in 26 variables, such that a given number k + 2 is prime if and only if that system has a solution in nonnegative integers: [7]