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c. 2800 BC — Indus Valley civilization on the Indian subcontinent, earliest use of decimal ratios in a uniform system of ancient weights and measures, the smallest unit of measurement used is 1.704 millimetres and the smallest unit of mass used is 28 grams. [citation needed]
Any such decimal fraction, i.e.: d n = 0 for n > N, may be converted to its equivalent infinite decimal expansion by replacing d N by d N − 1 and replacing all subsequent 0s by 9s (see 0.999... In summary, every real number that is not a decimal fraction has a unique infinite decimal expansion.
1698 (perhaps deriving from a much earlier use of middle dot to separate juxtaposed numbers) division slash (a.k.a. solidus ) 1718 (deriving from horizontal fraction bar, invented by Abu Bakr al-Hassar in the 12th century)
260 BC – Greece, Archimedes proved that the value of π lies between 3 + 1/7 (approx. 3.1429) and 3 + 10/71 (approx. 3.1408), that the area of a circle was equal to π multiplied by the square of the radius of the circle and that the area enclosed by a parabola and a straight line is 4/3 multiplied by the area of a triangle with equal base ...
The Hindu–Arabic system is designed for positional notation in a decimal system. In a more developed form, positional notation also uses a decimal marker (at first a mark over the ones digit but now more commonly a decimal point or a decimal comma which separates the ones place from the tenths place), and also a symbol for "these digits recur ad infinitum".
Sexagesimal numerals were a mixed radix system that retained the alternating bases of 10 and 6 that characterized tokens, numerical impressions, and proto-cuneiform numerical signs. Sexagesimal numerals were used in commerce, as well as for astronomical and other calculations.
The litre (1 dm 3) for volumes of liquid; The gramme, for mass—defined as the mass of one cubic centimetre of water; The franc, for currency. Historical note: only the metre and (kilo)gramme defined here went on to become part of later metric systems. Litres and to a lesser extent hectares (100 ares, or 1 hm 2) are still in use, but are not ...
Any odd number n may be constructed by the formula n = 2k + 1, for a suitable integer k. Starting with k = 0, the first non-negative odd numbers are {1, 3, 5, 7, ...}. Any even number m has the form m = 2 k where k is again an integer .