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  2. Percentile - Wikipedia

    en.wikipedia.org/wiki/Percentile

    Each standard deviation represents a fixed percentile. Thus, rounding to two decimal places, −3σ is the 0.13th percentile, −2σ the 2.28th percentile, −1σ the 15.87th percentile, 0σ the 50th percentile (both the mean and median of the distribution), +1σ the 84.13th percentile, +2σ the 97.72nd percentile, and +3σ the 99

  3. Simpson's rule - Wikipedia

    en.wikipedia.org/wiki/Simpson's_rule

    Composite Simpson's 3/8 rule is even less accurate. Integration by Simpson's 1/3 rule can be represented as a weighted average with 2/3 of the value coming from integration by the trapezoidal rule with step h and 1/3 of the value coming from integration by the rectangle rule with step 2h. The accuracy is governed by the second (2h step) term.

  4. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...

  5. Golden ratio - Wikipedia

    en.wikipedia.org/wiki/Golden_ratio

    The golden ratio's negative −φ and reciprocal φ−1 are the two roots of the quadratic polynomial x2 + x − 1. The golden ratio is also an algebraic number and even an algebraic integer. It has minimal polynomial. This quadratic polynomial has two roots, and. The golden ratio is also closely related to the polynomial.

  6. Fraction - Wikipedia

    en.wikipedia.org/wiki/Fraction

    To change ⁠ 1 / 3 ⁠ to a decimal, divide 1.000... by 3 (" 3 into 1.000... "), and stop when the desired accuracy is obtained, e.g., at 4 decimals with 0.3333. The fraction ⁠ 1 / 4 ⁠ can be written exactly with two decimal digits, while the fraction ⁠ 1 / 3 ⁠ cannot be written exactly as a decimal with a finite number of digits.

  7. Approximations of π - Wikipedia

    en.wikipedia.org/wiki/Approximations_of_π

    The 12 cells (0, ±5), (±5, 0), (±3, ±4), (±4, ±3) are exactly on the circle, and 69 cells are completely inside, so the approximate area is 81, and π is calculated to be approximately 3.24 because 81⁄52 = 3.24. Results for some values of r are shown in the table below: r. area. approximation of π. 2.

  8. Geometric series - Wikipedia

    en.wikipedia.org/wiki/Geometric_series

    The geometric series 1/4 + 1/16 + 1/64 + 1/256 + ... shown as areas of purple squares. Each of the purple squares has 1/4 of the area of the next larger square (1/2× 1/2 = 1/4, 1/4×1/4 = 1/16, etc.). The sum of the areas of the purple squares is one third of the area of the large square. Another geometric series (coefficient a = 4/9 and ...

  9. Percentage - Wikipedia

    en.wikipedia.org/wiki/Percentage

    The percent value can also be found by multiplying first instead of later, so in this example, the 50 would be multiplied by 100 to give 5,000, and this result would be divided by 1,250 to give 4%. To calculate a percentage of a percentage, convert both percentages to fractions of 100, or to decimals, and multiply them. For example, 50% of 40% is: