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  2. Density - Wikipedia

    en.wikipedia.org/wiki/Density

    Mathematically, density is defined as mass divided by volume: [1] =, where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume , [ 2 ] although this is scientifically inaccurate – this quantity is more ...

  3. Alcohol by volume - Wikipedia

    en.wikipedia.org/wiki/Alcohol_by_volume

    [1] [2] [3] It is defined as the number of millilitres (mL) of pure ethanol present in 100 mL (3.5 imp fl oz; 3.4 US fl oz) of solution at 20 °C (68 °F). The number of millilitres of pure ethanol is the mass of the ethanol divided by its density at 20 °C (68 °F), which is 0.78945 g/mL (0.82353 oz/US fl oz; 0.79122 oz/imp fl oz; 0.45633 oz ...

  4. Covariance - Wikipedia

    en.wikipedia.org/wiki/Covariance

    For two jointly distributed real-valued random variables and with finite second moments, the covariance is defined as the expected value (or mean) of the product of their deviations from their individual expected values: [3] [4]: 119

  5. Doubling time - Wikipedia

    en.wikipedia.org/wiki/Doubling_time

    For example, with an annual growth rate of 4.8% the doubling time is 14.78 years, and a doubling time of 10 years corresponds to a growth rate between 7% and 7.5% (actually about 7.18%). When applied to the constant growth in consumption of a resource, the total amount consumed in one doubling period equals the total amount consumed in all ...

  6. Average - Wikipedia

    en.wikipedia.org/wiki/Average

    The type of average taken as most typically representative of a list of numbers is the arithmetic mean – the sum of the numbers divided by how many numbers are in the list. For example, the mean or average of the numbers 2, 3, 4, 7, and 9 (summing to 25) is 5.

  7. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    Sum the digits of 500702: 5 + 0 + 0 + (7 + 0 + 2 = 9, which counts as 0) = 5 5 = 5, so there is a good chance that the prediction that 6,338 × 79 equals 500,702 is right. The same procedure can be used with multiple operations, repeating steps 1 and 2 for each operation.

  8. Finite difference coefficient - Wikipedia

    en.wikipedia.org/wiki/Finite_difference_coefficient

    For example, the third derivative with a second-order accuracy is ‴ () + (+) + (+) + (), where represents a uniform grid spacing between each finite difference ...

  9. Earth mass - Wikipedia

    en.wikipedia.org/wiki/Earth_mass

    The combined effect is a net loss of material, estimated at 5.5 × 10 7 kg (5.4 × 10 4 long tons) per year. This amount is 10 −17 of the total earth mass. [ citation needed ] The 5.5 × 10 7 kg annual net loss is essentially due to 100,000 tons lost due to atmospheric escape , and an average of 45,000 tons gained from in-falling dust and ...