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.
US Version
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 front of the V means one less than five.
VI = 6, VII = 7, and VIII = 8.
IX = 9, X = 10, and XI = 11.
UK Version
Here's a Roman-numeral refresher:
I = 1, II = 2 and III = 3.
IIII, however, does not equal 4.
IV = 4 and V = 5, so the I in front of the V means one less than five.
VI = 6, VII = 7 and VIII = 8.
IX = 9, X = 10 and XI = 11.
US Version
The answer should reveal itself if you understand Hint One and you're willing to look at things from various points of view.
UK Version
The answer should reveal itself if you understand Hint 1 and you're willing to look at things from various points of view.
US Version
As mentioned in Hint 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...
UK Version
What Hint 2 is basically telling you is to look at things from different directions...
Flip the equation upside down.
US Version
Well, would you look at that! You don't need to move any matches at all. The equation is completely valid as is!
UK Version
Well, would you look at that! You don't need to move any matches at all. The equation is completely valid as it 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!
