What is the sum of a 17-term arithmetic sequence where the first term is 8 and the last term is -88?

Question

What is the sum of a 17-term arithmetic sequence where the first term is 8 and the last term is -88?
Choose one answer.
A. -542
B. -680
C. -893
D. -954

Answer 1

The sum of an arithmetic sequence, when you know the first and last number and the number of terms is:

 

n(a₁ + a_n) / 2

 

n = number of terms

a₁ = first term

a_n = last term

 

So in this case it would be:

 

17 * [8 + (-88)] / 2

= 17 * (-80) / 2

= -680

 

So the answer is B