document.write( "Question 1171556: From Precious Mirror of the Four Elements ( 1303 A.D. ) . I take along a bottle with some wine in it for an excursion in the spring. On reaching a tavern, I double the bottle’s content and drink 1 9/10 dou in the tavern. After passing 4 taverns, the bottle is empty. How much wine was there at the beginning? Show your solutions. \n" ); document.write( "
Algebra.Com's Answer #796555 by ikleyn(52781)\"\" \"About 
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\n" ); document.write( "I take along a bottle with some wine in it for an excursion in the spring.
\n" ); document.write( "On reaching a tavern, I double the bottle’s content and drink 1 9/10 dou in the tavern.
\n" ); document.write( "After passing 4 taverns, the bottle is empty. How much wine was there at the beginning?
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\n" ); document.write( "\n" ); document.write( "            My interpretation of this problem is different from that of @ankor@dixie-net.com.\r
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\n" ); document.write( "\n" ); document.write( "            THEREFORE,  my solution and my answer are different.\r
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document.write( "We have a sequence of numbers  \"x%5B0%5D\", \"x%5B1%5D\", \"x%5B2%5D\", \"x%5B3%5D\", \"x%5B4%5D\".\r\n" );
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document.write( "\"x%5B0%5D\" is the amount of wine in the bottle originally.\r\n" );
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document.write( "\"x%5Bk%5D\" is the amount of wine in the bottle at the Exit     from the  k-th tavern \r\n" );
document.write( "                                (same as at the entering to   the (k+1)-th tavern), k = 1,2,3,4.\r\n" );
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document.write( "From the problem's condition, we have this recursive formula\r\n" );
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document.write( "    \"x%5Bk%2B1%5D\" = \"2%2Ax%5Bk%5D-1.9\",      (1)\r\n" );
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document.write( "which is the formal mathematical translation of the problem's description.\r\n" );
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document.write( "We are given that  \"x%5B4%5D\" = 0, and they want we find \"x%5B0%5D\".\r\n" );
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document.write( "Surely, the problem should be solved in a backward manner.\r\n" );
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document.write( "For it, I express \"x%5Bk%5D\" from (1) in this way\r\n" );
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document.write( "    \"x%5Bk%5D\" = \"%28x%5Bk%2B1%5D%2B1.9%29%2F2\"    (2)\r\n" );
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document.write( "Now I will go step by step BACKWARD from  k= 3  with  \"x%5B4%5D\" = 0.\r\n" );
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document.write( "In order for to facilitate my calculations, I use MS Excel in my computer with implemented formula (2) in it.\r\n" );
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document.write( "It provides all calculations in seconds, giving me THIS Table below\r\n" );
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document.write( "    k         \"x%5Bk%5D\"\r\n" );
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document.write( "--------------------------\r\n" );
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document.write( "    4		0\r\n" );
document.write( "    3		0.95\r\n" );
document.write( "    2		1.425\r\n" );
document.write( "    1		1.6625\r\n" );
document.write( "    0		1.78125\r\n" );
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document.write( "So, the ANSWER is: the initial amount of wine in the bottle was  1.78125  units of the volume.\r\n" );
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