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BEBRAS 2017 Grade 3-4 Round 2 Ext Question 7

BEBRAS · BEBRAS 2017 Grade 3-4 Round 2 Ext

Question 7

Four guests each bring one gift. Each gives a gift to one other guest, each receives exactly one gift, and nobody gives to themselves. Art→Bran means Art gives to Bran; Art→Bran, Cáit→Art describes two gifts.

Question illustration

Which arrangement obeys the rules?
  1. Art→Bran, Cáit→Dara, Dara→Bran, Bran→Art
  2. Cáit→Dara, Dara→Bran, Art→Cáit, Cáit→Art
  3. Dara→Bran, Art→Dara, Cáit→Art, Bran→Cáit
  4. Bran→Cáit, Cáit→Art, Dara→Bran, Art→Cáit