Question

find the sum of series 6 + 9 +12 .....upto 35 terms
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Answer 1

This is an AP
Here
a=6. d=9-6=3 n=35

Sn = n/2(2a+(n-1)d)
=35/2(12+34*3)
=35/2(12+102)
=35/2(114)
=35*57
=1995