Question

What is the sum of the arithmetic sequence 140, 135, 130 , if there are 35 terms?

Answer 1

If there are 35 terms, the last term will be 34 steps down from the first. The common difference is `-5`.

Explanation:

The last term will be `140-(34*5)=-30`

Calculating the sum:
You take the mean between the highest an lowest term, and multiply by the number of terms:

`Sum=(140+(-30))/2*35=1925`