In the Roman numerical system, what number do the letters M D represent?
And the answer is: 1,500.
In the Roman numerical system, the letter M represents 1,000, and the letter D represents 500. If you add them together, the answer is 1,500.
As one might guess, the Roman numerical system began in Ancient Rome. It first appeared around 800 or 900 B.C. and originated from a need to standardize counting for more effective communication and trade. Using one's hand could only take you up to ten, and oftentimes even that could be unclear. The Roman numerical method utilized the human hand as the standard of reference, but introduced letters and figures to make the process a bit more complex.
The Roman numerical "alphabet" is based off of seven standard symbols: I, V, X, L, D and M. These symbols are added together from left to right to achieve a specific amount. For Ancient Roman traders, a single finger or line represented "I", while "V" could be conveyed through 5 fingers or the V-shape between the thumb and forefinger. "X", meaning 10, equalled two hands (or ten fingers). Larger numbers were portrayed through more complex gestures based on subtle adjustments to the first ten gestures.
As you might guess, this practice soon became more confusing, complex, and overall limiting to the average trader. Fractions could not be shown through gesture, nor the number 0. Eventually, ancient traders abandoned the Roman numeral hand-system for the more complex and effective Hindu and Arabic number system. These ways of counting displayed numbers more closely to today's usage, where numbers are read as as single number in sequence (ex: 135 as one number).
That's not to say Roman numerals have fallen out of use altogether. These ancient numerals play select roles in modern day life, including but not limited to: major sporting events, some analog clocks, the titles of Monarchs (we see you, Queen Elizabeth II), and the prefaces of books.
And now, a joke:
I struggle with Roman numerals until I get to 159. And then it just CLIX!