Five identical glowing crystals are placed in a row on a shelf. Each minute, the middle crystal changes to the opposite color of its current state, while all other crystals remain unchanged. If all start out red, what is the exact color combination of the row after three minutes?
Red, Red, Blue, Red, Red
Let R = Red, B = Blue. Initially: R R R R R. Minute 1: Only the 3rd crystal flips, making it B. Row is R R B R R. Minute 2: Only the new middle (3rd) flips back to R. Row is R R R R R. Minute 3: The 3rd crystal flips to B again. Final row: R R B R R.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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