document.write( "Question 1207639: 75+72+69+66+.....21+18+15 \n" ); document.write( "

Algebra.Com's Answer #845615 by ikleyn(52781) $\"\"$ $\"About$

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document.write( "They want you find the sum of an arithmetic progression.\r\n" );
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document.write( "First term is 75; last term is 15; common difference is 3.\r\n" );
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document.write( "The sum is the product of the mean by the number of terms.\r\n" );
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document.write( "The mean is   =  = 45.\r\n" );
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document.write( "The number of gaps =  =  = 20.\r\n" );
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document.write( "The number of terms is 20+1 = 21.\r\n" );
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document.write( "The sum is  mean * the number of terms = 21 * 45 = 945.    ANSWER\r\n" );
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