Who is lying?
Ann says "Mine watch is showing 7.30." Betty says "Mine and Ann's watches are showing 7.30." Cintia says "Mine or Betty's watches are not showing 7.30." Only one of three friends is lying. Which one could be lying? If you are allowed to chose, which watch will you want to see, to be certain who is lying?
Teacher tip
Ann can not be lying, since in that case, Betty is lying too, and only one of three friends is lying. So, Ann speaks the truth and Ann's watch shows 7.30. If Betty is lying than Betty's watch does not show 7.30 and Cintia speaks the truth. If Betty speaks the truth, then Betty's watch shows 7.30, and if Cintia is lying, then Cintia's watch shows 7.30. So, either Betty is lying or Cintia is lying. If you are allowed to see Betty's watch, and if it shows 7.30, then Cintia is lying, and if Betty's watch does not show 7.30 then Betty is lying.
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