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Find the missing number (?) in the following sequence:

$$ 8 \ \ 35 \ \ 32 \ \ 4 \ \ 5 \ \ 32 \ \ 28 \ \ (?) \ \ 21 \ \ 12 \ \ 31 \ \ 29 $$

4 possibilities: $ \ -6, \ \ 3, \ \ 48, \ -2$

Explain why.

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closed as not a real question by t.b., Asaf Karagila, robjohn, Andres Caicedo, Qiaochu Yuan Mar 22 '12 at 19:45

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

18  
It is obviously 15. These are the ages of the members of my neighbour's family, when sorted by height. Yes, that 5 year old is tall! –  Aryabhata Mar 20 '12 at 21:27
2  
@TheChaz: I don't think there is any need to explain... –  Aryabhata Mar 20 '12 at 21:33
4  
To people flagging Aryabhata's comment: the comment is clearly a humourous way of putting forward the point that the question has no mathematical answer. –  Mariano Suárez-Alvarez Mar 20 '12 at 21:43
5  
It has no mathematical answer because we could construct a polynomio that agrees with all your given values, but takes upon any value in the place of $?$ –  Daniel Montealegre Mar 20 '12 at 21:55
6  
-1 for not showing that the original came as a matrix, which helps point toward the desired solution. –  Ross Millikan Mar 20 '12 at 22:56

1 Answer 1

up vote 1 down vote accepted

The proposed solution is rather ugly : $ \begin{array} {ccccc} 8&=&5&+&2&+1\\ 35&=&32&+&1&+2\\ 32&=&28&+&3&+1\\ 4&=&-6&+&2&+8\\ \end{array} $ $\ $rather sorry...

except that the last term is $29$ instead of $28$ in the link so that the answer should be... $-7$ ;-)

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so there is a mathematical answer! –  Adam Mar 20 '12 at 22:58
1  
There is no one single answer that can be found using mathematical reasoning alone. The sequence $8, 35, 32, 4, 5, 32, 28, 1000000000, 21, 12, 31, 29$ is perfectly valid, for example; the only thing wrong with it is that it's more complicated. Alternatively: the question "what number should fill in the blank?" is not a mathematical question, because "should" is not well-defined. –  Tanner Swett Mar 21 '12 at 19:09

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