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2005 AMC 10A Problems/Problem 9: Difference between revisions

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There is only <math>1</math> distinct arrangement that reads <math>XOXOX</math>
There is only <math>1</math> distinct arrangement that reads <math>XOXOX</math>


Therfore the desired probability is <math>\frac{1}{10} \Rightarrow B</math>
Therfore the desired [[probability]] is <math>\frac{1}{10} \Rightarrow \mathrm{(B)}</math>


==See Also==
==See Also==
Line 17: Line 17:


*[[2005 AMC 10A Problems/Problem 10|Next Problem]]
*[[2005 AMC 10A Problems/Problem 10|Next Problem]]
*[[Combination]]
[[Category:Introductory Combinatorics Problems]]

Revision as of 09:44, 2 August 2006

Problem

Three tiles are marked $X$ and two other tiles are marked $O$. The five tiles are randomly arranged in a row. What is the probability that the arrangement reads $XOXOX$?

$\mathrm{(A) \ } \frac{1}{12}\qquad \mathrm{(B) \ } \frac{1}{10}\qquad \mathrm{(C) \ } \frac{1}{6}\qquad \mathrm{(D) \ } \frac{1}{4}\qquad \mathrm{(E) \ } \frac{1}{3}$

Solution

There are $\frac{5!}{2!3!}=10$ distinct arrangments of three $X$'s and two $O$'s.

There is only $1$ distinct arrangement that reads $XOXOX$

Therfore the desired probability is $\frac{1}{10} \Rightarrow \mathrm{(B)}$

See Also

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