Enigma 1578: About turn
7 February 2012
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From New Scientist #2743, 16th January 2010 [link]
Joe placed six lettered counters on a 3-by-2 grid as shown, reading ENIGMA anticlockwise, and then he removed the E. Penny then slid the counters around, successively moving them up, down or across into a gap, so that after Joe replaced the E in its original position, the letters read ENIGMA clockwise.
What was the smallest number of counters that Penny needed to move to achieve this?