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	<id>http://mathpuzzlewiki.com/index.php?action=history&amp;feed=atom&amp;title=Turn_off_a_calculator</id>
	<title>Turn off a calculator - Revision history</title>
	<link rel="self" type="application/atom+xml" href="http://mathpuzzlewiki.com/index.php?action=history&amp;feed=atom&amp;title=Turn_off_a_calculator"/>
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	<updated>2026-04-05T04:52:09Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
	<generator>MediaWiki 1.44.0</generator>
	<entry>
		<id>http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=605&amp;oldid=prev</id>
		<title>Vampire Library at 01:39, 7 November 2010</title>
		<link rel="alternate" type="text/html" href="http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=605&amp;oldid=prev"/>
		<updated>2010-11-07T01:39:22Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&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 19:39, 6 November 2010&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-l1&quot;&gt;Line 1:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 1:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&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;{{Solution| Such a sequence is given by On--&amp;gt;On--&amp;gt;2nd--&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;turns it on &lt;/del&gt;and then turns it off &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;again&lt;/del&gt;. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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;{{Solution| Such a sequence is given by On--&amp;gt;On--&amp;gt;2nd--&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;again&lt;/ins&gt;. If the calculator is on then this sequence does nothing, &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;does nothing &lt;/ins&gt;and then turns it off. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vampire Library</name></author>
	</entry>
	<entry>
		<id>http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=604&amp;oldid=prev</id>
		<title>Vampire Library at 01:37, 7 November 2010</title>
		<link rel="alternate" type="text/html" href="http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=604&amp;oldid=prev"/>
		<updated>2010-11-07T01:37:46Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&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 19:37, 6 November 2010&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-l1&quot;&gt;Line 1:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 1:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&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;{{Solution| &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;The desired &lt;/del&gt;sequence is On--&amp;gt;On--&amp;gt;2nd--&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, turns it on and then turns it off again. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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;{{Solution| &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;Such a &lt;/ins&gt;sequence is &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;given by &lt;/ins&gt;On--&amp;gt;On--&amp;gt;2nd--&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, turns it on and then turns it off again. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vampire Library</name></author>
	</entry>
	<entry>
		<id>http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=603&amp;oldid=prev</id>
		<title>Vampire Library at 01:36, 7 November 2010</title>
		<link rel="alternate" type="text/html" href="http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=603&amp;oldid=prev"/>
		<updated>2010-11-07T01:36:47Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&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 19:36, 6 November 2010&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-l1&quot;&gt;Line 1:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 1:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;As you are finishing up your math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to begin with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is already on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&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;{{Solution| The desired sequence is On-&amp;gt;On-&amp;gt;2nd-&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, turns it on and then turns it off again. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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;{{Solution| The desired sequence is On&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;-&lt;/ins&gt;-&amp;gt;On&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;-&lt;/ins&gt;-&amp;gt;2nd&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;-&lt;/ins&gt;-&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, turns it on and then turns it off again. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vampire Library</name></author>
	</entry>
	<entry>
		<id>http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=602&amp;oldid=prev</id>
		<title>Vampire Library at 01:36, 7 November 2010</title>
		<link rel="alternate" type="text/html" href="http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=602&amp;oldid=prev"/>
		<updated>2010-11-07T01:36:24Z</updated>

		<summary type="html">&lt;p&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&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 19:36, 6 November 2010&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-l1&quot;&gt;Line 1:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 1:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&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;As you are finishing up &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;you &lt;/del&gt;math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;start &lt;/del&gt;with.  You know that the &quot;on&quot; button will turn the calculator on if it is off, but does nothing if the calculator is on.  To turn the calculator off, you must first press the &quot;2nd&quot; key, and then the &quot;on&quot; key.  However, if the calculator is off, the &quot;2nd&quot; key has no action.  Given that the calculator could be off, on, or on with the &quot;2nd&quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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;As you are finishing up &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;your &lt;/ins&gt;math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;begin &lt;/ins&gt;with.  You know that the &quot;on&quot; button will turn the calculator on if it is off, but does nothing if the calculator is &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;already &lt;/ins&gt;on.  To turn the calculator off, you must first press the &quot;2nd&quot; key, and then the &quot;on&quot; key.  However, if the calculator is off, the &quot;2nd&quot; key has no action.  Given that the calculator could be off, on, or on with the &quot;2nd&quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?   &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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; &lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&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;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;{{Solution| The desired sequence is On-&amp;gt;On-&amp;gt;2nd-&amp;gt;On. In the case that the calculator is already off this sequence turns it on, does nothing, and then turns it off. If the calculator is on then this sequence does nothing, turns it on and then turns it off again. Finally, if the calculator is on with the &quot;2nd&quot; key pressed this sequence turns it off, turns it on, and then turns it off. }}&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&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;[[Category: Computer science]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</summary>
		<author><name>Vampire Library</name></author>
	</entry>
	<entry>
		<id>http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=88&amp;oldid=prev</id>
		<title>Oscarlevin: Created page with &#039;As you are finishing up you math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the c…&#039;</title>
		<link rel="alternate" type="text/html" href="http://mathpuzzlewiki.com/index.php?title=Turn_off_a_calculator&amp;diff=88&amp;oldid=prev"/>
		<updated>2010-04-20T18:41:11Z</updated>

		<summary type="html">&lt;p&gt;Created page with &amp;#039;As you are finishing up you math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the c…&amp;#039;&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;As you are finishing up you math homework, the power goes out.  You realize that it might not come on for a while, so you should probably just call it quits.  You reach for the calculator to turn it off, but then realize that you are not sure whether it was on or off to start with.  You know that the &amp;quot;on&amp;quot; button will turn the calculator on if it is off, but does nothing if the calculator is on.  To turn the calculator off, you must first press the &amp;quot;2nd&amp;quot; key, and then the &amp;quot;on&amp;quot; key.  However, if the calculator is off, the &amp;quot;2nd&amp;quot; key has no action.  Given that the calculator could be off, on, or on with the &amp;quot;2nd&amp;quot; key already pressed, is there a sequence of button presses that will guarantee the calculator is off once finished?  &lt;br /&gt;
&lt;br /&gt;
[[Category: Computer science]]&lt;/div&gt;</summary>
		<author><name>Oscarlevin</name></author>
	</entry>
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