document.write( "Question 1196091: Please help with the homework:
\n" ); document.write( "At what compound interest rate per annum must money be invested if the principal must treble in ten years and interest is calculated monthly. \n" ); document.write( "

Algebra.Com's Answer #828787 by ikleyn(52775) $\"\"$ $\"About$

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\n" ); document.write( "Please help with the homework:
\n" ); document.write( "At what compound interest rate per annum must money be invested
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document.write( "Let \"r\" be the compound interest rate per annum.\r\n" );
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document.write( "Start from the formula for the future value\r\n" );
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document.write( "    3 =  = \r\n" );
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document.write( "Take logarithm base 10 of both sides of the equation\r\n" );
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document.write( "    log(3) = 120*log(1+r/12).\r\n" );
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document.write( "Find log(1+r/12) =  = 0.00397601.\r\n" );
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document.write( "It gives  1 + r =  = use your calculator = 1.009197137.\r\n" );
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document.write( "Hence,  r/12 = 1.009197137 - 1 = 0.009197137;  then  r = 12*0.009197137 = 0.110365644 = 0.1104 (rounded).\r\n" );
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document.write( "ANSWER.  The needed compound interest rate is about  11%  per annum (rounded).\r\n" );
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