document.write( "Question 1202030: In the year 2000 the population of the world was 6,1 billion. The doubling time of the world population is 20 years. In which year will the world population reach 100 billion if it continues to grow at the same rate? (You will need to use a calculator.) \n" ); document.write( "

Algebra.Com's Answer #836647 by ikleyn(52813) $\"\"$ $\"About$

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\n" ); document.write( "In the year 2000 the population of the world was 6,1 billion.
\n" ); document.write( "The doubling time of the world population is 20 years.
\n" ); document.write( "In which year will the world population reach 100 billion
\n" ); document.write( "if it continues to grow at the same rate? (You will need to use a calculator.)
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document.write( "Since we have the info about the doubling period, we write the growing exponential function\r\n" );
document.write( "for the population with the base of 2\r\n" );
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document.write( "    P(t) =  = 6.1*2^(t/20),\r\n" );
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document.write( "saying that the doubling period is 20 years.\r\n" );
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document.write( "Substitute 100 billions in the left side\r\n" );
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document.write( "    100 =  = 6.1*2^(t/20).\r\n" );
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document.write( "Divide both sides by 6.1\r\n" );
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document.write( "     = ,  or  16.39344262 = .\r\n" );
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document.write( "To solve this equation for t, take logarithm base 10 of both sides\r\n" );
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document.write( "    log(16.39344262) =  = (t/20)*log((2))\r\n" );
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document.write( "and express t\r\n" );
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document.write( "    t =  = 80.7009 years  (rounded).    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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\n" ); document.write( "\n" ); document.write( "If you want to see many other similar and different solved problems on population growth, look into the lesson\r
\n" ); document.write( "\n" ); document.write( " - Population growth problems \r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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