Art of Problem Solving

1991 AIME Problems/Problem 15: Difference between revisions

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== Problem ==
== Problem ==
For positive integer <math>n_{}^{}</math>, define <math>S_n^{}</math> to be the minimum value of the sum
For positive integer <math>n_{}^{}</math>, define <math>S_n^{}</math> to be the minimum value of the sum
<center><math>\sum_{k=1}^n \sqrt{(2k-1)^2+a_k^2},</math></center>
<math>\sum_{k=1}^n \sqrt{(2k-1)^2+a_k^2},</math>
where <math>a_1,a_2,\ldots,a_n^{}</math> are positive real numbers whose sum is 17. There is a unique positive integer <math>n^{}_{}</math> for which <math>S_n^{}</math> is also an integer. Find this <math>n^{}_{}</math>.
where <math>a_1,a_2,\ldots,a_n^{}</math> are positive real numbers whose sum is 17. There is a unique positive integer <math>n^{}_{}</math> for which <math>S_n^{}</math> is also an integer. Find this <math>n^{}_{}</math>.



Revision as of 17:32, 19 April 2007

Problem

For positive integer $n_{}^{}$, define $S_n^{}$ to be the minimum value of the sum $\sum_{k=1}^n \sqrt{(2k-1)^2+a_k^2},$ where $a_1,a_2,\ldots,a_n^{}$ are positive real numbers whose sum is 17. There is a unique positive integer $n^{}_{}$ for which $S_n^{}$ is also an integer. Find this $n^{}_{}$.

Solution

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See also

1991 AIME (ProblemsAnswer KeyResources)
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Problem 14
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