Question

Find the sum of the arithmetic series 7+13+...+601.

Answer 1

Explanation:

d=13-7=6

Let number of terms=n

l=a+(n-1)d

601=7+(n-1)6

601=7+6n-6

601=6n+1

6n=601-1=600

n=600/6=100

`s_(n)=(n)/(2) (a1+an)\\=(100)/(2)(7+601)\\=50 * 608\\=30400`