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	<id>https://gradwiki.math.ucr.edu/index.php?action=history&amp;feed=atom&amp;title=Answer</id>
	<title>Answer - Revision history</title>
	<link rel="self" type="application/atom+xml" href="https://gradwiki.math.ucr.edu/index.php?action=history&amp;feed=atom&amp;title=Answer"/>
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	<updated>2026-05-20T07:51:51Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
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	<entry>
		<id>https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=655&amp;oldid=prev</id>
		<title>Ryan Moruzzi: Challenge Problem Solutions</title>
		<link rel="alternate" type="text/html" href="https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=655&amp;oldid=prev"/>
		<updated>2015-05-02T17:32:51Z</updated>

		<summary type="html">&lt;p&gt;Challenge Problem Solutions&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left diff-editfont-monospace&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 17:32, 2 May 2015&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l2&quot; &gt;Line 2:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 2:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In order for no cats to collide, all four cats must walk in the same direction.  Thus, all four cats must walk clockwise OR all four cats must walk counterclockwise.  This means &amp;lt;math&amp;gt;P(no cats collide) = P(&amp;lt;&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;text&lt;/del&gt;&amp;gt;all cats go clockwise&amp;lt;&lt;del class=&quot;diffchange diffchange-inline&quot;&gt;/text&lt;/del&gt;&amp;gt;) + P(all cats go counterclockwise)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In order for no cats to collide, all four cats must walk in the same direction.  Thus, all four cats must walk clockwise OR all four cats must walk counterclockwise.  This means &amp;lt;math&amp;gt;P(&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;/math&amp;gt;&lt;/ins&gt;no cats collide&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;math&amp;gt;&lt;/ins&gt;) = P(&amp;lt;&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;/math&lt;/ins&gt;&amp;gt;all cats go clockwise&amp;lt;&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;math&lt;/ins&gt;&amp;gt;) + P(&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;/math&amp;gt;&lt;/ins&gt;all cats go counterclockwise&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;math&amp;gt;&lt;/ins&gt;)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The probability a cat chooses clockwise or counterclockwise is &amp;lt;math&amp;gt;1/2&amp;lt;/math&amp;gt;.  So the probability all four cats choose clockwise or counterclockwise is &amp;lt;math&amp;gt;(1/2)*(1/2)*(1/2)*(1/2)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The probability a cat chooses clockwise or counterclockwise is &amp;lt;math&amp;gt;1/2&amp;lt;/math&amp;gt;.  So the probability all four cats choose clockwise or counterclockwise is &amp;lt;math&amp;gt;(1/2)*(1/2)*(1/2)*(1/2)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Therefore, &amp;lt;math&amp;gt;P(no cats collide) = (1/2)*(1/2)*(1/2)*(1/2) + (1/2)*(1/2)*(1/2)*(1/2) = 1/16 + 1/16 = 1/8.&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Therefore, &amp;lt;math&amp;gt;P(&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;/math&amp;gt;&lt;/ins&gt;no cats collide&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;math&amp;gt;&lt;/ins&gt;) = (1/2)*(1/2)*(1/2)*(1/2) + (1/2)*(1/2)*(1/2)*(1/2) = 1/16 + 1/16 = 1/8.&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Ryan Moruzzi</name></author>
	</entry>
	<entry>
		<id>https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=654&amp;oldid=prev</id>
		<title>Ryan Moruzzi: /* Challenge Problem 2 Solution */</title>
		<link rel="alternate" type="text/html" href="https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=654&amp;oldid=prev"/>
		<updated>2015-05-02T17:31:10Z</updated>

		<summary type="html">&lt;p&gt;&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;Challenge Problem 2 Solution&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;
&lt;table class=&quot;diff diff-contentalign-left diff-editfont-monospace&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;en&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 17:31, 2 May 2015&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l2&quot; &gt;Line 2:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 2:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt;−&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In order for no cats to collide, all four cats must walk in the same direction.  Thus, all four cats must walk clockwise OR all four cats must walk counterclockwise.  This means &amp;lt;math&amp;gt;P(no cats collide) = P(all cats go clockwise) + P(all cats go counterclockwise)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt;+&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;In order for no cats to collide, all four cats must walk in the same direction.  Thus, all four cats must walk clockwise OR all four cats must walk counterclockwise.  This means &amp;lt;math&amp;gt;P(no cats collide) = P(&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;text&amp;gt;&lt;/ins&gt;all cats go clockwise&lt;ins class=&quot;diffchange diffchange-inline&quot;&gt;&amp;lt;/text&amp;gt;&lt;/ins&gt;) + P(all cats go counterclockwise)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The probability a cat chooses clockwise or counterclockwise is &amp;lt;math&amp;gt;1/2&amp;lt;/math&amp;gt;.  So the probability all four cats choose clockwise or counterclockwise is &amp;lt;math&amp;gt;(1/2)*(1/2)*(1/2)*(1/2)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;The probability a cat chooses clockwise or counterclockwise is &amp;lt;math&amp;gt;1/2&amp;lt;/math&amp;gt;.  So the probability all four cats choose clockwise or counterclockwise is &amp;lt;math&amp;gt;(1/2)*(1/2)*(1/2)*(1/2)&amp;lt;/math&amp;gt;.   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Therefore, &amp;lt;math&amp;gt;P(no cats collide) = (1/2)*(1/2)*(1/2)*(1/2) + (1/2)*(1/2)*(1/2)*(1/2) = 1/16 + 1/16 = 1/8.&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class='diff-marker'&gt; &lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Therefore, &amp;lt;math&amp;gt;P(no cats collide) = (1/2)*(1/2)*(1/2)*(1/2) + (1/2)*(1/2)*(1/2)*(1/2) = 1/16 + 1/16 = 1/8.&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Ryan Moruzzi</name></author>
	</entry>
	<entry>
		<id>https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=653&amp;oldid=prev</id>
		<title>Ryan Moruzzi: Challenge Problem Answers</title>
		<link rel="alternate" type="text/html" href="https://gradwiki.math.ucr.edu/index.php?title=Answer&amp;diff=653&amp;oldid=prev"/>
		<updated>2015-05-02T17:29:58Z</updated>

		<summary type="html">&lt;p&gt;Challenge Problem Answers&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;==Challenge Problem 2 Solution==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
In order for no cats to collide, all four cats must walk in the same direction.  Thus, all four cats must walk clockwise OR all four cats must walk counterclockwise.  This means &amp;lt;math&amp;gt;P(no cats collide) = P(all cats go clockwise) + P(all cats go counterclockwise)&amp;lt;/math&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
The probability a cat chooses clockwise or counterclockwise is &amp;lt;math&amp;gt;1/2&amp;lt;/math&amp;gt;.  So the probability all four cats choose clockwise or counterclockwise is &amp;lt;math&amp;gt;(1/2)*(1/2)*(1/2)*(1/2)&amp;lt;/math&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Therefore, &amp;lt;math&amp;gt;P(no cats collide) = (1/2)*(1/2)*(1/2)*(1/2) + (1/2)*(1/2)*(1/2)*(1/2) = 1/16 + 1/16 = 1/8.&amp;lt;/math&amp;gt;&lt;/div&gt;</summary>
		<author><name>Ryan Moruzzi</name></author>
	</entry>
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