Algebra.Com's Answer #854069 by ikleyn(53742)![\"\"](\"/images/stars/stars-13.gif\")  
You can put this solution on YOUR website!
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document.write( "if the U.S grows at an annual rate of 7.5%, how long will take to reach a population of 400 000 000?
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document.write( "(the population, now, is 300 000 000)
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document.write( " The solution in the post is incorrect conceptually.
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document.write( " It is incorrect, since it uses a linear model, while an exponential model must be used.\r
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document.write( " See my correct solution below.\r
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document.write( "Use exponential function for the population\r\n" );
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document.write( " P(t) =  =  .\r\n" );
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document.write( "Then you have this equation to find 't', the time from \"now' in years\r\n" );
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document.write( " 400000000 = .\r\n" );
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document.write( "Divide both sides by 300000000\r\n" );
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document.write( "  =  .\r\n" );
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document.write( "Take logarithm of both sides\r\n" );
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document.write( "  = t*log((1.075)}}}\r\n" );
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document.write( "Express 't' and calculate\r\n" );
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document.write( " t =  = 3.977868374.\r\n" );
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document.write( "Rounding, you may say that the process will take about 3.98 years (or 4 years).\r\n" );
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document.write( "In reality, the average percentage growing population US in the last 10-15 years (2010 - 2025) \r\n" );
document.write( "is about 1% (or below it).\r\n" );
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document.write( "Solved correctly.\r
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