# Roman Numeral Twist

You probably already know about this; in fact, I numbered my number tricks with Roman numerals on the Math Trick Menu!

## This is the Roman numeral for 4: IV

## And this is the Roman numeral for 6: VI

## And this is the Roman numeral for 9: IX

## And this is the Roman numeral for 11: XI

## And this is the Roman numeral for 40: XL

## And this is the Roman numeral for 60: LX

## And this is the Roman numeral for 90: XC

## And this is the Roman numeral for 110: CX

## And this is the Roman numeral for 400: CD

## And this is the Roman numeral for 600: DC

## And this is the Roman numeral for 900: CM

## And this is the Roman numeral for 1,100: MC

Did you notice how the letters switched places for each 2nd numeral? I call this the Roman Numeral Twist!

## You can use addition or subtraction to "twist" the numerals so the letters switch places! The number you must add or subtract is:

## 2 × 10^x

### Or maybe since we're using Roman numerals, I should print it like this:

## II * X^p

(I replaced the "x" multiplication symbol with an asterisk & the exponent variable "x" with a lowercase P to prevent confusion with the "X" Roman numeral for number 10.) The exponent must be an __integer!__

Do you understand the logic with the Roman numerals at the top of this Web page? The numbers **4, 6, 9 & 11** × **10 to the power of an integer of your choice** is printed using this logic:

*Subtract if the smaller numeral is at the left of the bigger one; add if the smaller numeral is at the right of the bigger one.*

__Here comes the math!__

## IV + II = VI & VI - II = IV

## IX + II = XI & XI - II = IX

## XL + XX = LX & LX - XX = XL

## XC + XX = CX & CX - XX = XC

## CD + CC = DC & DC - CC = CD

## CM + CC = MC & MC - CC = CM

What about Roman numerals for numbers greater than or equal to 4,000? There's another Web page on the Math Trick Menu with more information. See "Why Numbers Are Important".

## Here's the Roman numeral for 3,999:

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© Derek Cumberbatch