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Four Corners (Posted on 2004-07-17) Difficulty: 3 of 5
On each corner of a square is a quarter. Your task is to have all four quarter heads-up or tails-up at the end of a turn.

You are blindfolded at the start, and you do not know which are heads-up and which are tails-up. Each turn, you may flip however many of them you want and then ask if you are done (and no, you cannot tell, by touch, whether it is heads- or tails-up). The square is then rotated a random, undisclosed number of quarter spins (multiple of 90 degrees), and you may take another turn.

Minimize the maximum number of turns required to be assured you will complete the task.

No Solution Yet Submitted by red_sox_fan_032003    
Rating: 4.2500 (8 votes)

Comments: ( You must be logged in to post comments.)
  Subject Author Date
7 moves plus 1 to see if it started solvedtanx2005-11-07 18:45:05
re(3): Good startKen Haley2004-09-08 01:08:05
re(2): Good starthelen2004-09-04 11:43:52
re: Good startKen Haley2004-08-24 23:54:34
Looks like it only takes 7 moves.Ken Haley2004-08-24 01:29:51
re: Good startCharlie2004-07-17 15:18:30
Some ThoughtsGood startTristan2004-07-17 13:31:26
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