document.write( "Question 838572: The first term of an AP is 6 and the fifth term is 12. The progression has n terms and the sum of all the terms is 90. \r
\n" ); document.write( "\n" ); document.write( "What is the value of n? (how many terms) \n" ); document.write( "
Algebra.Com's Answer #505173 by mananth(16946)\"\" \"About 
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The first term of an AP is 6 and the fifth term is 12. The progression has n terms and the sum of all the terms is 90. \r
\n" ); document.write( "\n" ); document.write( "What is the value of n? (how many terms)\r
\n" ); document.write( "\n" ); document.write( "Tn = a+(n-1)d\r
\n" ); document.write( "\n" ); document.write( "a=6 ,
\n" ); document.write( "T5 = 12\r
\n" ); document.write( "\n" ); document.write( "12=6+(5-1)d\r
\n" ); document.write( "\n" ); document.write( "12=6+4d\r
\n" ); document.write( "\n" ); document.write( "12-6=4d
\n" ); document.write( "6=4d
\n" ); document.write( "d=3/2\r
\n" ); document.write( "\n" ); document.write( "Tn = 90\r
\n" ); document.write( "\n" ); document.write( "90=6+(n-1)*1.5\r
\n" ); document.write( "\n" ); document.write( "90-6= 1.5n -1.5\r
\n" ); document.write( "\n" ); document.write( "84+1.5=1.5n\r
\n" ); document.write( "\n" ); document.write( "85.5/1.5 = n\r
\n" ); document.write( "\n" ); document.write( "57 = n\r
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