<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><div><div><div><span class="Apple-style-span" style="font-size: 18px;"></span></div><div style="font-size: medium; "><div><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; "><br></span></span></div><div><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; ">This file may be opened with </span></span><span class="Apple-style-span" style="font-size: 18px; ">Excel, Open Office or Google Docs.</span></div></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; "><br></span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; ">The first project we would like to suggest is to just repeat the calculation we show, using one or more of the applications in Plan Ceibal´ computers.</span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><br></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; ">Then, it could be resolving other problems:</span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; "><br></span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; ">- Given seven of the eight digits in an ID card, calculate the missing digit.</span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; "><br></span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><span style="color: rgb(0, 0, 0); background-color: transparent; font-variant: normal; text-decoration: none; vertical-align: baseline; ">- Whenever there is an error, is the calculation going to return the wrong control digit? Justify the answer.</span></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><br></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; ">- If we transpose two consecutive digits, a very frequent error, will the calculation result change? Are we going to be able, in such case, to find out what the error was and correct it?</span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><br></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; ">- Are there other applications in the real world for control digits, besides the ID card?</span></div></div></div></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; "><br></span></div><div style="font-size: medium; "><span class="Apple-style-span" style="font-size: 18px; ">We will be glad to send the paper by Omar Gil and Ricardo Vilaró, mentioned in the attached spreadsheet, to anyone who might wish to further study the subject and do other exercises.</span></div><div><span class="Apple-style-span" style="font-size: 18px; "><b><font class="Apple-style-span" color="#ff1314"><br></font></b></span></div><div><span class="Apple-style-span" style="font-size: 18px; "><b><font class="Apple-style-span" color="#ff1314"><br></font></b></span></div><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Arial; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div>Carlos Rabassa</div><div>Volunteer</div><div>Plan Ceibal Support Network</div><div>Montevideo, Uruguay</div><div><a href="http://www.tiny.cc/AprendoILearn">www.tiny.cc/AprendoILearn</a></div></span><br class="Apple-interchange-newline"> </div> <br></div></body></html>