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  2. Approximations of π - Wikipedia

    en.wikipedia.org/wiki/Approximations_of_π

    He also gave two other approximations of π: π ≈ 22 ⁄ 7 and π ≈ 355 ⁄ 113, which are not as accurate as his decimal result. The latter fraction is the best possible rational approximation of π using fewer than five decimal digits in the numerator and denominator. Zu Chongzhi's results surpass the accuracy reached in Hellenistic ...

  3. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million (ppm, 10 ...

  4. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

  5. Circular error probable - Wikipedia

    en.wikipedia.org/wiki/Circular_error_probable

    The relation between and are given by the following table, where the values for DRMS and 2DRMS (twice the distance root mean square) are specific to the Rayleigh distribution and are found numerically, while the CEP, R95 (95% radius) and R99.7 (99.7% radius) values are defined based on the 68–95–99.7 rule

  6. Approximation error - Wikipedia

    en.wikipedia.org/wiki/Approximation_error

    Best rational approximants for π (green circle), e (blue diamond), ϕ (pink oblong), (√3)/2 (grey hexagon), 1/√2 (red octagon) and 1/√3 (orange triangle) calculated from their continued fraction expansions, plotted as slopes y/x with errors from their true values (black dashes)

  7. Sieve analysis - Wikipedia

    en.wikipedia.org/wiki/Sieve_analysis

    A sieve analysis (or gradation test) is a practice or procedure used in geology, civil engineering, [1] and chemical engineering [2] to assess the particle size distribution (also called gradation) of a granular material by allowing the material to pass through a series of sieves of progressively smaller mesh size and weighing the amount of material that is stopped by each sieve as a fraction ...

  8. Milü - Wikipedia

    en.wikipedia.org/wiki/Milü

    It is within 0.000 009 % of the value of π, or in terms of common fractions overestimates π by less than ⁠ 1 / 3 748 629 ⁠. The next rational number (ordered by size of denominator) that is a better rational approximation of π is ⁠ 52 163 / 16 604 ⁠ , though it is still only correct to six decimal places.

  9. Rounding - Wikipedia

    en.wikipedia.org/wiki/Rounding

    Approximating an irrational number by a fraction π: 22/7 1-digit-denominator Approximating a rational number by a fraction with smaller denominator 399 / 941 3 / 7 1-digit-denominator Approximating a fraction by a fractional decimal number: 5 / 3 1.6667: 4 decimal places: Approximating a fractional decimal number by one with fewer digits 2.1784