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BEBRAS 2017 Grade 9-10 Round 2 Ext Question 13

BEBRAS · BEBRAS 2017 Grade 9-10 Round 2 Ext

Question 13

In a classification diagram, a line from a lower group to an upper group means every member of the lower group also belongs to the upper group. For example, all Snakes are Reptiles, and some Mammals are not Mice. The first tree has Vertebrates above Mammals and Reptiles; Mammals above Carnivora and Rodents; Carnivora above Bears and Dogs; Rodents above Mice and Beavers; Reptiles above Turtles and Snakes.

Question illustration

The second diagram shows analogous groups on planet Morgenstern.

Question illustration

Alice: “Every Basti is Seiokronto.” Benjamin: “Some Hontraruru are not Semememi.” What can we say about their statements?

Editorial spelling clarification: Alice's printed “Seiokronto” refers to the node printed “Seiokrontro” in the diagram.
  1. Both tell the truth
  2. Only Benjamin tells the truth
  3. Only Alice tells the truth
  4. Neither tells the truth