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  2. Modular arithmetic - Wikipedia

    en.wikipedia.org/wiki/Modular_arithmetic

    In chemistry, the last digit of the CAS registry number (a unique identifying number for each chemical compound) is a check digit, which is calculated by taking the last digit of the first two parts of the CAS registry number times 1, the previous digit times 2, the previous digit times 3 etc., adding all these up and computing the sum modulo 10.

  3. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    Used to measure the time between alternating power cycles. Also a casual term for a short period of time. centisecond: 10 −2 s: One hundredth of a second. decisecond: 10 −1 s: One tenth of a second. second: 1 s: SI base unit for time. decasecond: 10 s: Ten seconds (one sixth of a minute) minute: 60 s: hectosecond: 100 s: milliday: 1/1000 d ...

  4. Mean time between failures - Wikipedia

    en.wikipedia.org/wiki/Mean_time_between_failures

    Mean time between failures (MTBF) describes the expected time between two failures for a repairable system. For example, three identical systems starting to function properly at time 0 are working until all of them fail. The first system fails after 100 hours, the second after 120 hours and the third after 130 hours.

  5. Multiplication - Wikipedia

    en.wikipedia.org/wiki/Multiplication

    Area of a cloth 4.5m × 2.5m = 11.25m 2; 4 ⁠ 1 / 2 ⁠ × 2 ⁠ 1 / 2 ⁠ = 11 ⁠ 1 / 4 ⁠ Multiplication (often denoted by the cross symbol × , by the mid-line dot operator ⋅ , by juxtaposition, or, on computers, by an asterisk * ) is one of the four elementary mathematical operations of arithmetic, with the other ones being addition ...

  6. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    If one has a two-digit number, take it and add the two numbers together and put that sum in the middle, and one can get the answer. For example: 24 x 11 = 264 because 2 + 4 = 6 and the 6 is placed in between the 2 and the 4. Second example: 87 x 11 = 957 because 8 + 7 = 15 so the 5 goes in between the 8 and the 7 and the 1 is carried to the 8.

  7. Decimal time - Wikipedia

    en.wikipedia.org/wiki/Decimal_time

    The time between each gēng is 1⁄10 of a day, making a gēng 2.4 hours—or 2 hours 24 minutes—long As a 10-part system, the gēng are strongly associated with the 10 celestial stems, especially since the stems are used to count off the gēng during the night in Chinese literature.

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  9. Equation of time - Wikipedia

    en.wikipedia.org/wiki/Equation_of_time

    The equation of time describes the discrepancy between two kinds of solar time. The word equation is used in the medieval sense of "reconciliation of a difference". The two times that differ are the apparent solar time , which directly tracks the diurnal motion of the Sun , and mean solar time , which tracks a theoretical mean Sun with uniform ...