theory pages added

theory/roman.en.html

@@ -0,0 +1,11 @@
+<h3>Roman Numerals</h3>
+<p>Roman numerals originated in ancient Rome and remained the standard way of writing numbers throughout Europe well into the Middle Ages. They use combinations of letters from the Latin alphabet.</p>
+<h3>Symbols</h3>
+<div class="theory-example">I = 1    V = 5    X = 10    L = 50    C = 100    D = 500    M = 1000</div>
+<h3>How it works</h3>
+<p>Roman numerals are primarily additive: values are summed left to right. However, a smaller value placed before a larger one indicates subtraction:</p>
+<div class="theory-example">IV = 5 − 1 = 4    IX = 10 − 1 = 9<br>XL = 50 − 10 = 40    XC = 100 − 10 = 90    CM = 1000 − 100 = 900</div>
+<h3>Examples</h3>
+<div class="theory-example">XLII = 40 + 2 = 42<br><br>MCMXCIV = 1000 + 900 + 90 + 4 = 1994</div>
+<h3>Rules</h3>
+<p>Roman numerals can represent numbers from 1 to 3999. I, X, C, and M can be repeated up to three times. V, L, and D are never repeated. The subtractive combinations IV, IX, XL, XC, CM, and CD are the only allowed subtractions.</p>