Based on the relation between the numbers of each shape, find the number for the question mark.

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  1. 337
  2. 339
  3. 549
  4. 569

Source: Iraninan Ph.D University Enterance 2017


1 Answer 1


The answer:



The inside number's leftmost digit is the highest factor of the top number. Middle digit is the highest factor of bottom left number. Right digit is highest factor of bottom right number.

So 15 => 5, 12 => 6, 18 => 9

  • $\begingroup$ I would say that it's the highest "proper divisor", it's terminology for a factor that isn't the number itself $\endgroup$
    – Quintec
    Commented Feb 15, 2018 at 18:27

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