Question

How do you find Sn for the arithmetic series given a1=4, a_n=100# and n=25?

Answer 1

Here, a1=4 ; an=100 ; n=25

Let l be the nth term

Now, Sn = n/2[a+l]

=25/2[4+100]

=25/2×104

=25×52

=1300

Hence , Sn = 1300