Art of Problem Solving

2006 AMC 12B Problems/Problem 25: Difference between revisions

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== Problem ==
== Problem ==
{{problem}}
A sequence <math>a_1,a_2,\dots</math> of non-negative integers is defined by the rule <math>a_{n+2}=|a_{n+1}-a_n|</math> for <math>n\geq 1</math>. If <math>a_1=999</math>, <math>a_2<999</math> and <math>a_{2006}=1</math>, how many different values of <math>a_2</math> are possible?
 
<math>
\mathrm{(A)}\ 165
\qquad
\mathrm{(B)}\ 324
\qquad
\mathrm{(C)}\ 495
\qquad
\mathrm{(D)}\ 499
\qquad
\mathrm{(E)}\ 660
</math>


== Solution ==
== Solution ==

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Problem

A sequence $a_1,a_2,\dots$ of non-negative integers is defined by the rule $a_{n+2}=|a_{n+1}-a_n|$ for $n\geq 1$. If $a_1=999$, $a_2<999$ and $a_{2006}=1$, how many different values of $a_2$ are possible?

$\mathrm{(A)}\ 165 \qquad \mathrm{(B)}\ 324 \qquad \mathrm{(C)}\ 495 \qquad \mathrm{(D)}\ 499 \qquad \mathrm{(E)}\ 660$

Solution

http://www.unl.edu/amc/mathclub/5-0,problems/H-problems/H-pdfs/2006/HB2006-25.pdf

See also

2006 AMC 12B (ProblemsAnswer KeyResources)
Preceded by
Problem 24
Followed by
Last Question
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All AMC 12 Problems and Solutions