数字与罗马数字互相转换
Numbers above 3,999 use vinculum notation: a line above a numeral multiplies its value by 1,000.
So XLIXDCLXXXII = 49,682.
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Fibonacci's Sales Pitch
Fibonacci didn't invent Hindu-Arabic numerals — they originated in India around 500 AD. But his 1202 book Liber Abaci was essentially a 600-page argument that these new numbers were better for business. He showed European merchants how place value and zero could transform trade and banking. He was right. By 1500, the debate was over.
Read more →The Subtraction Rule: Elegant Shorthand
The subtraction rule is what makes Roman numerals clever rather than just tedious. Instead of writing IIII for 4, you write IV: "one before five." Instead of DCCCC for 900, you write CM: "one hundred before one thousand." Only six subtractive pairs exist (IV, IX, XL, XC, CD, CM), and once you know them, you can read any Roman numeral instantly.
Read more →罗马数字从何而来？
人们认为罗马数字起源于手势和计数标记。笔画I代表一根手指，V代表拇指和手指之间表示五的间隔，X代表交叉的双手表示十。字母L、C、D和M来自希腊字母chi、theta和phi的变体，分别代表50、100、500和1,000。随着时间推移，这些标记演变成了今天人们所熟知的拉丁字母。罗马字母表中没有0，因为数字0的概念直到印度在大约公元600年 / 10600 HE发明之后才完全发展起来。