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posted by vinay Monday, July 4, 2011 at 5:01am.
What is the sum to 15 terms of an arithmetic progression whose 8th term is 4?
W.k.t, Sn = n/2 {2a + (n-1)d} then S15 = 15/2 {2a + 14d} =15/2 {2(a+7d)} wkt, a+7d = 15 S15 = 15(15)=225
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