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Find the missing integer.

  1. Jul 17, 2012 #1


    What are people's opinion on these two questions?

    The obvious answer for the first question (5) seems too simple, as it merely stems from the observation that the last number in the first two rows happen to be the average of the first three. I'm not sure if the real solution is this easy though.. or maybe I'm just thinking too much.

    The second question, I have absolutely no idea about.

    Any comments, suggestions, etc, are appreciated.
  2. jcsd
  3. Jul 17, 2012 #2
    All I've noticed so far is that in the second figure, for some reason the top row, second column, and first diagonal from the top each adds to 13.
  4. Sep 18, 2012 #3
    In both figures the top square adds to 21 2+7+9+3=9+4+6+2
    The left figure bottom square 3+7+6+6 adds to 22.
    The right bottom square with the given numbers 2+7+2 adds to 11.
    Subtracting the 5 from the sum in the first figure yields 17.
    Subtracting 3 from 11 yields 8.
    9 would work as an answer using this logic.
    Last edited: Sep 18, 2012
  5. Oct 25, 2012 #4
    I also got
    But I got it through this method:
    If you separate the image into 4 triangles, consisting of the numbers 7,5,4; 5,9,2; 6,6,4; and 3,4,?; you will notice that the complete triangles add up to 16 in each case, continuing on that idea, logically, the missing number is 9.

    I just noticed that the two pictures are separate, and that the OP's solution to the first problem makes more sense.
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