document.write( "Question 40398: Ryan was 8 when his parents invested $4000 in a certificateof deposite that pays 6% for investments of 3 years. If Ryan leaves the account alone until it reaches $10,000, how old will he be? ---won't he be 20??? \n" ); document.write( "
Algebra.Com's Answer #25799 by mbarugel(146)\"\" \"About 
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Hello!
\n" ); document.write( "The following rules applies for investmentes:\r
\n" ); document.write( "\n" ); document.write( "Future Value = Current Value*(1 + r)^n\r
\n" ); document.write( "\n" ); document.write( "where r is the interest rate in decimal form (in your case, 6% would be 0.06) and n is the number of periods over which interest is accrued. So we have to find out how many periods (years) it will take for $4,000 to become $10,000. So we solve the equation:\r
\n" ); document.write( "\n" ); document.write( "\"10000+=+4000%2A%281+%2B+0.06%29%5En\"
\n" ); document.write( "\"10000+=+4000%2A%281.06%29%5En\"\r
\n" ); document.write( "\n" ); document.write( "We have to isolate n. In order to do it, we take natural logarithm of both sides:\r
\n" ); document.write( "\n" ); document.write( "\"ln%2810000%29+=+ln%284000%2A%281.06%29%5En%29\"
\n" ); document.write( "\"ln%2810000%29+=+ln%284000%29+%2B+ln%28%281.06%29%5En%29\"
\n" ); document.write( "\"ln%2810000%29+=+ln%284000%29+%2B+n%2Aln%281.06%29\"
\n" ); document.write( "\"n+=+%28ln%2810000%29-ln%284000%29%29%2Fln%281.06%29\"
\n" ); document.write( "\"n+=+15.72\"\r
\n" ); document.write( "\n" ); document.write( "si it will take about 15.72 yeras for $4,000 to become $10,000 at a 6% interest rate. Since Ryan was 8 when the investment was made, he will be 23.72 years (almost 24) old when the acct reaches $10,000\r
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\n" ); document.write( "\n" ); document.write( "I hope this helps!
\n" ); document.write( "Get more answers at Online Math Answers.com!
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