document.write( "Question 555690: If Joelle invests $8000 into a retirement account with a 9% interest rate compounded monthly, how long will it take until this single payment has grown in her account to $16,000?
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Algebra.Com's Answer #361986 by lwsshak3(11628)\"\" \"About 
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If Joelle invests $8000 into a retirement account with a 9% interest rate compounded monthly, how long will it take until this single payment has grown in her account to $16,000?
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\n" ); document.write( "Compound Interest Formula: A=P(1+i)^n, P=initial investment, i=interest rate per period, n=number of periods, A=amount after n periods.
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\n" ); document.write( "For given problem:
\n" ); document.write( "P=Initial investment=$8000
\n" ); document.write( "i=interest rate per month=.09/12=.0075
\n" ); document.write( "A=amount after n months=$16000
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\n" ); document.write( "16000=8000*(1+.0075)^n
\n" ); document.write( "16000=8000(1.0075)^n
\n" ); document.write( "16000/8000=(1.0075)^n
\n" ); document.write( "2=(1.0075)^n
\n" ); document.write( "take log of both sides
\n" ); document.write( "log(2)=n*log(1.0075)
\n" ); document.write( "n=log(2)/log(1.0075)
\n" ); document.write( "n≈93.77
\n" ); document.write( "ans: It will take about 94 months for Joelle's account to grow to $16,000. \n" ); document.write( "
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