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missing number

How to solve these missing number questions, and what logic should be applied to solve these type of questions?

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closed as off-topic by Rubio Feb 14 '18 at 20:19

  • This question does not appear to be about creation and solving of puzzles, within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hello and welcome to Puzzling SE. Do take a look at the tour page to get yourself better acquainted with the site, its rules and standards. For instance, this seems to be puzzles 11 and 12 from some other source. Nothing wrong in that (provided you're allowed to share it by the author), but PSE requires that you provide attribution for the source - either a URL, or the book title/author, etc. $\endgroup$ – Phylyp Feb 14 '18 at 5:24
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    $\begingroup$ From the phrasing I'd assumed the OP is actually asking for guidance on how to approach such things (perhaps some hints on what is expected) rather than presenting these as puzzles to solve, i.e. not (misre)presenting them as their own work. $\endgroup$ – Will Crawford Feb 14 '18 at 13:22
  • $\begingroup$ @WillCrawford Even when asking for guidance, for content that the poster did not create themselves, we require they provide attribution - at minimum they need to let us know where this came from (and any additional context they can provide is usually a big help to solvers). Posts which use someone else's content without disclosing where it came from are generally deleted. $\endgroup$ – Rubio Feb 14 '18 at 20:18
  • $\begingroup$ I'm putting this question on hold until proper attribution of its original source is provided. This looks like you're asking us to solve a puzzle you found elsewhere. For content that you did not create yourself, please provide attribution - at minimum you need to let us know where this came from, and any additional context you can provide is usually a big help to solvers. Posts which use someone else's content without disclosing where it came from are generally deleted. $\endgroup$ – Rubio Feb 14 '18 at 20:19
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First Answer :

8, 1
Logic: The phrasing of the question (number instead of numbers) provides the clue that each pair of digits in a row forms a two-digit number.
So representing the grid as two-digit numbers we have:

73, 46, 19 (delta -27)
11, 9, 7 (delta -2)
52, 42, 32 (delta -10)
99, 50, 1 (delta -49)
67, 82, 97 (delta 15)
15, 48, 81 (delta 33)

Second Answer may be :

Answer : 7
Logic : In each row of the diagram, the central value equals the sum of the differences between the left hand pair of numbers and the right hand pair of numbers.

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  • $\begingroup$ I believe your second answer is the intended one. Funny thing is that for every row you could also do (A-B)-(C-D)=E. It holds perfectly, but the answer would then have to be 1, which is not among the possibilities. $\endgroup$ – slvrbld Feb 14 '18 at 15:30
  • $\begingroup$ @slvrbld I think the two ways are equivalent: $$c=(a-b)+(d-e) \implies c+e=(a-b)+d \implies e=(a-b)+(d-c) \implies e=(a-b)-(c-d)$$ It doesn't hold in the last case, but it can be fixed by adding some absolute values. $\endgroup$ – internet_user Feb 14 '18 at 16:19
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partial answer

8,1 for the first one. The three pairs of digits on each line form arithmetic progressions.

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