document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=745077>Question 745077</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help If the number of terms of an Arithmetic sequence is 15 and the value of it's middle term is 10 then find the sum of it's terms is there any rule that i can solve it with?? Thanks </SPAN>\n" );
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document.write( "The nth term of an AP is given by the formula Tn = a+(n-1)d\r<BR>\n" );
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document.write( "t15 = a+14d\r<BR>\n" );
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document.write( "The middle term is the 8th term\r<BR>\n" );
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document.write( "T8=a+7d\r<BR>\n" );
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document.write( "10=a+7d<BR>\n" );
document.write( "multiply by 2\r<BR>\n" );
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document.write( "20=2(a+7d)<BR>\n" );
document.write( "20=2a+14d\r<BR>\n" );
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document.write( "Sum of n terms = Sn = n/2[2a+(n-1)d]\r<BR>\n" );
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document.write( "s15 = 15/2[2a+(15-1)d]\r<BR>\n" );
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document.write( "S15= 15/2[2a+14d]\r<BR>\n" );
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document.write( "but 2a+14d=20\r<BR>\n" );
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document.write( "S15=15/2( 20)\r<BR>\n" );
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document.write( "S15=150\r<BR>\n" );
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document.write( "sum of 15 terms = 150 </SPAN>\n" );
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