Question 21
The source asks: “A number from 1 to 9 is filled into each circle below, such that the sum of 4 numbers on any face is the same and cannot divide 45. Which number cannot be used?” Analyse whether these printed conditions determine a unique unused number, and justify your conclusion.
Source ambiguity: the text does not explicitly forbid repeated numbers and its face-sum condition may be incomplete. For this analysis, use each chosen number at most once; keep “cannot divide 45” in its literal sense. Explain the information limitation instead of guessing a missing condition.
Source ambiguity: the text does not explicitly forbid repeated numbers and its face-sum condition may be incomplete. For this analysis, use each chosen number at most once; keep “cannot divide 45” in its literal sense. Explain the information limitation instead of guessing a missing condition.