by simple observation... the common terms to the AP's are 21, 41,...
So Sn = 100(2*21 + 99*20)/2
consider the A.P's 17,21,25...and 16,21,26.......Find the sum of first 100 common terms appearing in the two series.
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1 Answers
Asish Mahapatra
·2009-04-08 02:30:10