document.write( "Question 830326: A girl is the eldest of 15 children and each child is exactly a year and a half apart. The eldest is eight times the youngest age. What is the oldest age? \n" ); document.write( "
Algebra.Com's Answer #500538 by Edwin McCravy(20056)\"\" \"About 
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A girl is the eldest of 15 children and each child is exactly a year and a half apart.
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document.write( "Their ages form an arithmetic sequence with n=15 terms and common\r\n" );
document.write( "difference d=1.5.  So we use the formula:\r\n" );
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document.write( "an = a1 + (n-1)d\r\n" );
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document.write( "a15 = a1 + (15-1)(1.5)\r\n" );
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document.write( "a15 = a1 + (14)(1.5)\r\n" );
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document.write( "a15 = a1 + 21\r\n" );
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\n" ); document.write( "The eldest is eight times the youngest age
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document.write( "The eldest's age is a15\r\n" );
document.write( "The youngest's age is a1\r\n" );
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document.write( "So we have the system of two equations in two unknowns: \r\n" );
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document.write( "\"system%28a%5B15%5D+=+a%5B1%5D+%2B+21%2Ca%5B15%5D+=+8a%5B1%5D%29\"  \r\n" );
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document.write( "Solve by substitution or elimination and get\r\n" );
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document.write( "a1 = 3 and a15 = 24\r\n" );
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document.write( "The youngest is 3 and the eldest is 24\r\n" );
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document.write( "-------------------------\r\n" );
document.write( "Checking:\r\n" );
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document.write( "Their ages are \r\n" );
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document.write( "3, 4.5, 6, 7.5, 9, 10.5, 12, 13.5, 15, 16.5, 18, 19.5, 21, 22.5, 24\r\n" );
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document.write( "That's 15 ages, all 1.5 years apart and 24 is 8 times 3.\r\n" );
document.write( "So it checks.\r\n" );
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document.write( "Edwin
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