[UF148] Matchstick Math

Matchstick Math (Mathematchsticks in the UK version) is a puzzle in Professor Layton and the Unwound Future.

Puzzle

US Version

The math equation below is written in matchsticks! Read as Roman numerals, it means 1 + 11 = 10.

To make this a valid equation, what's the fewest number matches that you need to move?

UK Version

Here's an equation that's been written using matches. Read as Roman numerals, it means: 1 + 11 = 10.

What's the minimum number of matches you need to move to make this equation valid?

Hints

Click a Tab to reveal the Hint.

Here's a Roman-numeral primer:

I = 1, II = 2, and III = 3.
IIII, however, does not equal four.
IV = 4 and V = 5, so the I in from of the V means one less than five.
VI = 6, VII = 7, and VIII = 8.
IX = 9, X = 10, and XI = 11.

The answer should reveal itself if you understand Hint One and you're willing to look at things from various points of view.

As mentioned in Hing Two, it's important to "look at things from various points of view." In other words, don't be afraid to turn this problem on its head...

Flip the equation upside down.

Well, would you look at that! You don't need to move any matches at all. The equation is completely valid at is!

Solution

Incorrect

Too bad!

There's a twist here somewhere...

Correct

You're on fire!

Zero matches is correct.

If you look at the equation upside down, it becomes 10 = 9 + 1 in Roman numerals.

US Version

The phrase "fewest number of matches" might have tricked you into thinking "at least one match," but "fewest" can mean no matches at all!

UK Version

The phrase "minimum number" might have tricked you into thinking "at least one match", but "minimum number" can mean moving no matches at all!

A big thanks to http://professorlayton3walkthrough.blogspot.com

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Puzzle

Hints

Solution

Incorrect

Correct