Difference between revisions of "2005 AMC 10A Problems/Problem 9"

(Problem)
(Solution)
Line 7: Line 7:
 
There are <math>\frac{5!}{2!3!}=10</math> distinct arrangements of three <math>X</math>'s and two <math>O</math>'s.  
 
There are <math>\frac{5!}{2!3!}=10</math> distinct arrangements of three <math>X</math>'s and two <math>O</math>'s.  
  
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>.
  
Therefore the desired [[probability]] is <math>\boxed{\frac{1}{10}} \Rightarrow \mathrm{(B)}</math>
+
Therefore the desired [[probability]] is <math>\boxed{\textbf{(B) }\frac{1}{10}}</math>
  
 
==See also==
 
==See also==

Revision as of 11:01, 13 December 2021

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 $XOXOX$?

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

Solution

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

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

Therefore the desired probability is $\boxed{\textbf{(B) }\frac{1}{10}}$

See also

2005 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 8
Followed by
Problem 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AMC 10 Problems and Solutions

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png