document.write( "Question 205056: How many terms of the arithmetic sequence 2, 4, 6, 8, ... add up to 60,762? Can anyone help me with the answer and how you solved for it? I am confused and have gotten several different answers trying to do this problem. Thank you \n" ); document.write( "
Algebra.Com's Answer #154789 by scott8148(6628) You can put this solution on YOUR website! there is a \"canned\" formula; but if you look at what's going on, it is pretty straightforward\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the difference between consecutive terms in this sequence is 2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the first term is 2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "let X be the number of terms it takes to sum to 60762\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the value of the nth term is 2n\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the sum of the 1st and last terms is 2 + 2X \n" ); document.write( "the sum of the 2nd and next to last terms is 4 + (2X-2) or 2X + 2 \n" ); document.write( "the sum of the 3rd and second to last trems is 6 + (2X-4) or 2X + 2 \n" ); document.write( "this pattern is consistent \n" ); document.write( "the number of pairs is HALF the number of terms\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "so the sum of X terms of the sequence is (2X + 2)(X / 2) or X^2 + X\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "X^2 + X = 60762 ___ X (X + 1) = 60762 \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "so you are looking for two factors of 60762 that are one number apart \n" ); document.write( "___ the values are close to the square root of 60762 \n" ); document.write( "___ 246 and 247\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "246 terms \n" ); document.write( " |