Biggest Roman Number
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). Four plaques read XC, LX, CX and XL. Which number is the biggest?
Which number is the BIGGEST?
A smaller letter in front means subtract.
CX
XC = 90, LX = 60, CX = 110, XL = 40. CX wins.
How to solve it
Turn each plaque into an ordinary number, then compare. The rule: read left to right; if a letter is smaller than the one after it, subtract it, otherwise add it.
XC: X (10) comes before the bigger C (100), so it subtracts. 100 − 10 = 90.
LX: L (50) is followed by the smaller X (10), so both add. 50 + 10 = 60.
CX: C (100) is followed by the smaller X (10), so both add. 100 + 10 = 110.
XL: X (10) comes before the bigger L (50), so it subtracts. 50 − 10 = 40.
In order: 40, 60, 90, 110. The biggest is CX, which is 110.
The common wrong answer is XC, because it contains C, the largest letter on show, and it is easy to read it as 110. Its X sits in front, so it takes 10 away and gives 90. CX and XC use the same two letters, and only the order decides whether X adds or subtracts.
Takeaway: where the smaller letter stands matters more than which letters appear.
