The sum of the first 15 terms of an arithmetic sequence is 480. Find the 8th term of the sequence.

Given:

The sum of the first 15 terms of an arithmetic sequence is 480.

To find:

The 8th term of the sequence.

Solution:

We have,

We know that, the nth term of an AP is

Where, a is the first term and d is the common difference.

Putting n=8, we get the 8th term of the sequence.

The sum of first n terms is

Where, a is the first term and d is the common difference.

Divide both sides by 15.

Therefore, the 8th term of the arithmetic sequence is 32.

arithmetic sequence

step-by-step explanation:

given that a sequence has terms as

19, 15, 11,

this is represented on a graph

the pattern indicates that the sequence is an arithmetic sequence with i term

a=19 and common difference d =-4

any general term

thus the sequence is reduced by 4 for each successive term starting from 1 and nth term is

24-5n.

first negative term would start after 5th term

5th term =24-25< 0

from 5th term onwards the sequence would be negative.

the correct is answer is a 9-sided polygon!