document.write( "Question 992185: The Question: $6734 is deposited into a savings account at 4% interest, compounded monthly. To the nearest year, how long will it take for the account balance to reach $1,000,000?\r
\n" ); document.write( "\n" ); document.write( "The question is multiple choice, but when I work it out my answer fits none of the choices.\r
\n" ); document.write( "\n" ); document.write( "My solution:
\n" ); document.write( "A = P (1 + r/m)^n
\n" ); document.write( "A = 1,000,000
\n" ); document.write( "P = 6,734
\n" ); document.write( "r = 4% = 0.04
\n" ); document.write( "m = 12
\n" ); document.write( "n = 12n\r
\n" ); document.write( "\n" ); document.write( "1,000,000 = 6734 (1 + 0.04/12)^12n\r
\n" ); document.write( "\n" ); document.write( "I divide both sides by 6734 cancelling out the number on the right side leaving me with:\r
\n" ); document.write( "\n" ); document.write( "1,000,000/6734 = (1 + 0.04/12)^12n\r
\n" ); document.write( "\n" ); document.write( "148.500 = (1.003)^12n\r
\n" ); document.write( "\n" ); document.write( "I take the LOG of both sides.\r
\n" ); document.write( "\n" ); document.write( "LOG 148.500 = 12n LOG (1.003)\r
\n" ); document.write( "\n" ); document.write( "I divide both sides by 12 LOG (1.003) isolating n. Leaving me with:\r
\n" ); document.write( "\n" ); document.write( "n = LOG 148.500/12 LOG (1.003)\r
\n" ); document.write( "\n" ); document.write( "n = 139.11\r
\n" ); document.write( "\n" ); document.write( "My answer: Approximately 139 years.\r
\n" ); document.write( "\n" ); document.write( "Am I doing something wrong? I just started learning about LOG. Maybe I'm working the problem out wrong.
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Algebra.Com's Answer #611798 by solver91311(24713)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "You are doing the problem correctly, but I suspect you have an arithmetic error.\r
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\n" ); document.write( "\n" ); document.write( "Check your calculator work; you should get 125 and change.\r
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\n" ); document.write( "\n" ); document.write( "I figured out where you went wrong. You rounded off too soon when you calculated \r
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\n" ); document.write( "\n" ); document.write( "Using 1.003 in the calculation gives you 139 and change. Using 1.00333... to as many digits as your calculator will keep gives you 125.22+. Object lesson: Never round off until the last step in a multi-step calculation.\r
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\n" ); document.write( "\n" ); document.write( "John
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\n" ); document.write( "My calculator said it, I believe it, that settles it\r
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