Question

two arithmetic sequence questions. Help?

What is the common difference of a 43-term arithmetic sequence where the first term is -13 and the sum is 9,374?
A.11
B.11.5
C.12
D.12.5

What is the sum of a 14-term arithmetic sequence where the last term is 30 and the common difference is -5?
A.875
B.812.5
C.455
D.422.5

Answer 1

Sum of an arithmetic sequence = (first term + last term) / 2 * number of terms.
Plug the values and figure out the last term.
Since there are 43 terms, the last term is the 43rd term.
The nth term of an arithmetic sequence = a1 + (n-1)d
plug in the values and find d.

Answer 2

@aum can you work on one so i can see how they are worked out?