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Friday, March 20, 2009

Finish the Square

Logically, what number should replace the ?

6 8 12
10 2 5
15 4 ?

3 comments:

  1. 15 is the answer.

    Going either from top to bottom or from left two right along any column or any row, respectively, the third number is the product of the first and second numbers divided by four.

    For example, the rows are:
    6 * 8 = 48 / 4 = 12
    10 * 2 = 20 / 4 = 5
    15 * 4 = 60 / 4 = 15

    and the columns are:
    6 * 10 = 60 / 4 = 15
    8 * 2 = 16 / 4 = 4
    12 * 5 = 60 / 4 = 15.

    ReplyDelete
  2. 15 is the answer. As oudeis explained, the rows and columns all work out to x*y/4.

    ReplyDelete

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