Thomas (boggyb) wrote,

  • Music:

Brainteaser answer

Several people came up with solutions to yesterday's puzzle that only required moving one matchstick, but only one person found the real answer. For reference, the equation was this:

I + XI = X

And the challenge was to work out what the fewest numbers of moves was required to make a valid equation.

delta_mike spotted the obvious solution of moving the second I to the far right, giving I + X = XI (this is the one I tried originally). talismancer came up with a slight variation on this as well.

Bonus marks to omgimsuchadork for the inventive answer of moving the I to create I + XI ≠ X

One guy at work found yet another 1-move solution: I - XI = -X

Of course, this is a trick question and so none of those are correct. The correct answer is none, and bragging rights to the_s_guy for spotting that.

The solution is to rotate the surface your matchsticks are on (or walk round to the other side of the table), giving X = IX + I which is 10 = 9 + 1 and so is correct.

I actually didn't solve this by working that out - I saw that I could do it with 1 move, mistakenly assumed that it wasn't a trick question (I should have known better by then), and so entered 1 as my answer. When the game rejected it I then entered 0, as if it takes less than 1 move then there's only one possible answer left.
Tags: nablopomo

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