Posted by vinay on Monday, July 4, 2011 at 5:01am.
What is the sum to 15 terms of an arithmetic progression whose 8th term is 4?

arithmetic  subbu, Tuesday, February 14, 2017 at 7:26pm
W.k.t,
Sn = n/2 {2a + (n1)d} then
S15 = 15/2 {2a + 14d}
=15/2 {2(a+7d)}
wkt, a+7d = 15
S15 = 15(15)=225