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The square mile (abbreviated as sq mi and sometimes as mi2)〔Rowlett, Russ (September 1, 2004). ("S", ''How Many? A Dictionary of Units of Measurement'' ). University of North Carolina at Chapel Hill. Retrieved February 22, 2012.〕 is an imperial and US unit of measure for an area equal to the area of a square of one statute mile. It should not be confused with ''miles square'', which refers to the number of miles on each side squared. For instance, 20 miles square (20 × 20 miles) is equal to 400 square miles; an area of 10 × 40 miles is likewise 400 square miles, but it is not 20 miles square. One square mile is equal to: *4,014,489,600 square inches *27,878,400 square feet〔 *3,097,600 square yards〔 *640 acres〔 *2560 roods A square mile is equivalent to the following metric system measures:- *25,899,881,103.36 square centimetres *2,589,988.110336 square metres *258.9988110336 hectares *2.589988110336 square kilometres When applied to a portion of the earth's surface, which is curved rather than flat, "square mile" is an informal synonym for section. Romans derived measurements from marching. Five feet was equal to one pace (which is appropriately a double step). 1,000 paces measured a Roman mile which is very close to the British mile as used in 21st century. This Roman system was adopted, with local variations, throughout Europe as the Roman Empire spread.〔(【引用サイトリンク】url=http://www-history.mcs.st-and.ac.uk/HistTopics/Measurement.html )〕 Total population in a square mile is derived by dividing the total number of residents by the number of square miles of land area in the specified geographic area. The population per square kilometer is derived by multiplying the population per square mile by .3861.〔(【引用サイトリンク】title=Land Area and Persons Per Square Mile )〕 Land area measurements are originally recorded as whole square meters. Square meters are converted to square kilometers by dividing by 1,000,000; square kilometers are converted to square miles by dividing by 2.58999; square meters are converted to square miles by dividing by 2,589,988.〔 ==References== * (Formula Conversion, Square miles to numerous area units with algebraic steps and unit cancellation shown ) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「square mile」の詳細全文を読む スポンサード リンク
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