Answer:
3225
Step-by-step explanation:
The sum to n terms of an arithmetic sequence is
=
[ 2a + (n - 1)d ]
where a is the first term and d the common difference
here a = 6 and
d = 13 - 6 = 20 - 13 = 7, hence
=
[ (2 × 6) + (29 × 7) ]
= 15(12 + 203) = 15 × 215 = 3225