| Sabrina, There are 6 pairs per week, and after 11 weeks every two people will have lunched together exactly once.  Here is a schedule. The 12 positions in each sequence are the 12 people. The numbers indicate who lunches who with who that lunch day. The zeros lunch together, the ones, etc. 
  Day 1 :   (0, 1, 0, 1, 2, 3, 2, 3, 4, 5, 4, 5)Day 2 :   (0, 1, 1, 0, 2, 3, 3, 2, 4, 5, 5, 4)
 Day 3 :   (0, 1, 2, 3, 0, 1, 4, 5, 2, 3, 4, 5)
 Day 4 :   (0, 1, 2, 3, 1, 0, 4, 5, 3, 2, 5, 4)
 Day 5 :   (0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 0, 1)
 Day 6 :   (0, 1, 2, 3, 3, 2, 4, 5, 5, 4, 1, 0)
 Day 7 :   (0, 1, 2, 3, 4, 5, 0, 1, 4, 5, 2, 3)
 Day 8 :   (0, 1, 2, 3, 4, 5, 1, 0, 5, 4, 3, 2)
 Day 9 :   (0, 1, 2, 3, 4, 5, 2, 3, 0, 1, 4, 5)
 Day 10 : (0, 1, 2, 3, 4, 5, 3, 2, 1, 0, 5, 4)
 Day 11 : (0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5)
 Happy eating!--Victoria
 |