Question

in an A.P.,given
a10=47,a=2 find S12

Answer 1

T

10

=47=2+(10−1)d

47=2+9d

d=5

S

n

=a∗n+

2

d∗n(n−1)

S

15

=2∗15+

2

5∗15∗14

=30+525=555

Answer 2

so, s12 = 354

hope it was helpful