document.write( "Question 1178219: Find how long it takes a $2800 investment to double if it is invested at 9% compounded quarterly. \n" ); document.write( "
Algebra.Com's Answer #807407 by ikleyn(52776)\"\" \"About 
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document.write( "The standard translation of the words to Math is THIS equation\r\n" );
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document.write( "    2P = \"P%2A%281%2B0.09%2F4%29%5E%284%2At%29\",     (1)\r\n" );
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document.write( "where P is the principal amount, t is the time in years.\r\n" );
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document.write( "Canceling P in both sides, you get this equation\r\n" );
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document.write( "    2 = \"%281%2B0.09%2F4%29%5E%284t%29\"            (2)\r\n" );
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document.write( "with one unknown \"t\".\r\n" );
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document.write( "The standard method to solve it is to take logarithm of both sides.\r\n" );
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document.write( "It gives \r\n" );
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document.write( "    log(2) = 4t*log(1+0.09/4),\r\n" );
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document.write( "    \r\n" );
document.write( "    t = \"log%28%282%29%29%2F%284%2Alog%28%281%2B0.09%2F4%29%29%29\" = 7.78.      \r\n" );
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document.write( "Now you need to round this number to the nearest greater integer in order for the bank\r\n" );
document.write( "was in position to make the last compounding.\r\n" );
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document.write( "ANSWER.  8 years is required.\r\n" );
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\n" ); document.write( "\n" ); document.write( "To see many other similar (and different) solved problems, look into the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Compound interest percentage problems \r
\n" ); document.write( "\n" ); document.write( "    - Problems on discretely compound accounts \r
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\n" ); document.write( "\n" ); document.write( "After reading these lessons,  you will tackle such problems on your own without asking for help from outside.\r
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\n" ); document.write( "\n" ); document.write( "Also,  you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this online textbook under the topic \"Logarithms\".\r
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\n" ); document.write( "\n" ); document.write( "Save the link to this online textbook together with its description\r
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\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-I
\n" ); document.write( "https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson\r
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\n" ); document.write( "\n" ); document.write( "to your archive and use it when it is needed.\r
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\n" ); document.write( "\n" ); document.write( "Happy learning (!)\r
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