Use the sequence feature of a graphing calculator to evaluate the sum of the first 10 terms of the arithmetic sequence.
Round to the nearest thousandth, if necessary.
-A stack of poles has 39 poles in the bottom row, 38 poles in the next row, and so on, with 6 poles in the top row. How many poles are there in the stack?
A) 765
B) 759
C) 690
D) 771

Question

Quizplus · Accepted Answer

The sum of an arithmetic sequence can be found using the formula $S_n = \frac{n}{2}(a_1 + a_n)$, where $S_n$ is the sum of the first $n$ terms, $a_1$ is the first term, $a_n$ is the nth term, and $n$ is the number of terms. Here, $a_1 = 39$, $a_n = 6$, and $n = 34$ (since the sequence goes from 39 down to 6, which is 34 terms). Plugging these values into the formula gives $S_n = \frac{34}{2}(39 + 6) = 17 \times 45 = 765$.

Use the Sequence Feature of a Graphing Calculator to Evaluate