Roman Subtraction
Read the puzzle
A key shows Roman letter values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. A smaller letter after a bigger one adds; a smaller letter before a bigger one subtracts (VI = 6). What is LIV minus XLIV, written in Roman numerals?
What is LIV − XLIV, in Roman numerals?
Turn both into ordinary numbers first.
X
LIV = 54 and XLIV = 44. 54 − 44 = 10, which is X.
How to solve it
Convert both numerals to ordinary numbers, subtract, then convert back.
LIV: L is 50. Then IV, where I (1) stands before the bigger V (5), so it means 5 − 1 = 4. LIV = 50 + 4 = 54.
XLIV: XL has X (10) before the bigger L (50), so it means 50 − 10 = 40. Then IV = 4. XLIV = 40 + 4 = 44.
Subtract: 54 − 44 = 10.
Convert back: 10 in Roman numerals is a single X.
A common slip is adding every letter without the subtract rule: LIV becomes 50 + 1 + 5 = 56 and XLIV becomes 10 + 50 + 1 + 5 = 66, and the difference turns negative, which signals a misreading. Another is answering in ordinary digits when the question asks for Roman numerals; the Roman form of 10 is X.
Quick check: X + XLIV should give LIV. 10 + 44 = 54, and LIV is 54.
