Sep 11, 2021
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 ]
If you add this up, one plus two plus three plus four, adds up to 10.
The question is, can you move one matchstick, without removing it, still using them all -- and make that equal to four?
RAY: The challenge is to 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 four! A lot of people have trouble with this because of the idea of putting a negative sign in front.