Question

What is the sum of ten terms of a finite arithmetic series if the first term is 13 and the last term is 89?

A. 500
B. 520
C. 490
D. 510

Answer 1

Formula for the sum of n terms of a finite arithmetic series is

`S_n=(a_1+a_n)/(2)\cdot n.`

If
`n=10,\ a_1=13,\ a_(10)=89,` then

`S_(10)=(13+89)/(2)\cdot 10=51\cdot 10=510.`

Answer: 510.