More Matchstick Mathematics

Feb 16, 2002

RAY: Go out and get yourself 16 matchsticks. You're going to use the matchsticks to make the following Roman numeral sequence. One, then two matchsticks to make a plus sign. Plus Roman numeral two. Plus Roman numeral three. Plus Roman numeral four, which is not "IV," but, in this case, "IIII."

[For the Car Talk Puzzler Psychic Friends Network, that equation would be: I + II + III + IIII ]

TOM: If you add this up, one plus two plus three plus four, it adds up to 10.

RAY: Right. The question is, can you move one matchstick, without removing it, still using them all -- and make that equal to four?


RAY: Anyway, the question was move and reuse one matchstick to make this sum equal not to 10, but to four. And what you do is you take the plus sign between the one and the two, take the vertical matchstick, and put it horizontally in front of the one, so now the thing reads minus one, minus two, plus three plus four equals what?

TOM: Oh, four.

RAY: And a lot of people have trouble with this because the idea of putting a negative sign in front.

TOM: Yeah, I had trouble with that. Sixth grade, seventh grade, eighth grade, ninth grade.

RAY: That encompassed 12 years. Anyway, do we have a winner?

TOM: You bet we have a winner. The winner is Sue Goodney from Bloomington, Indiana.

Get the Car Talk Newsletter