Puzzle 2

Discussion in 'Physics & Math' started by chikis, Mar 6, 2014.

  1. chikis Registered Senior Member

    Messages:
    328
    Example 1

    12|16|20[10] 22

    Example 2

    1|3|5[2 1/2] 3 1/2

    Example 3

    30|40|50[15] 65

    Can you use the examples to find x?

    12|16|x[0] 32
     
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  3. rpenner Fully Wired Valued Senior Member

    Messages:
    4,833
    Find the pattern isn't math. Absent a model, there are always an infinite number of ways to predict a missing value.

    For this sequence a|b|c[r]s we have the following seemingly significant relationships:

    2b = a + c = r + s
    b - a = c - b

    which are consistent with x = 20

    And we have (2r -a)(2r - c) = 0 which is consistent with x = 0. But the same evidence for (2r -a)(2r - c) = 0 also supports (2r -a)(2r - c)(r) = 0 which is consistent with x = 20 .

    And we have (2s - 2b - c)(2s - 4b + c) = 0 which is consistent with x = 32. But the same evidence for (2s - 2b - c)(2s - 4b + c) = 0 also supports (2s - 2b - c)(2s - 4b + c)(2s - 4b) = 0 which is consistent with x = 20 .

    This hypothesis equivalent to a claim the pattern has 3 degrees of freedom (o, p, q)
    a = p + q
    b = 2p + q
    c = 3p + q
    r = p - o
    s = 3 p + 2 q + o

    p : q : o : a | b | c [ r ] s
    4 : 8 : -6 : 12 | 16 | 20 [ 10 ] 22
    2 : -1 : -1/2 : 1 : 3 : 5 [ 5/2 ] 7/2
    10 : 20 : -5 : 30 : 40 : 50 [ 15 ] 65
    4 : 8 : 4 : 12 | 16 | 20 [ 0 ] 32

    A useful puzzle would either give more examples or have less degrees of freedom.

    Finally -- it was entirely unnecessary to start a new thread for this.
     
    Last edited: Mar 7, 2014
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