document.write( "Question 935889: The seventh term of arithmetic progression series is 29 and the eleventh term is 54. Determine the sixteenth term. \n" ); document.write( "
Algebra.Com's Answer #569273 by rothauserc(4718)\"\" \"About 
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arithmetic progression series is defined by the following formula,
\n" ); document.write( "Xn = X1 + d*(n-1) where n is the nth term, X1 is the first term, d is common difference between terms. The problem gives us two formulas
\n" ); document.write( "X7 = X1 + d*(7-1) = 29
\n" ); document.write( "X11 = X1 + d*(11-1) = 54
\n" ); document.write( "combine like terms in both equations
\n" ); document.write( "X1 + 6d = 29
\n" ); document.write( "X1 + 10d = 54
\n" ); document.write( "subtract equation 1 from equation 2
\n" ); document.write( "4d = 25
\n" ); document.write( "d = 6.25
\n" ); document.write( "substitute for d in first equation
\n" ); document.write( "X1 + 6*6.25 = 29
\n" ); document.write( "X1 = 29 - 37.5 = -8.5
\n" ); document.write( "now calculate the 16th term
\n" ); document.write( "X16 = -8.5 + 6.25 * (16-1) = 85.25
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