Question

Determine the number of terms n : a 1 = 15, a n = 79, S n = 423

Answer 1

Answer:

The number of terms in the sequence is 9

Step-by-step explanation:

We want to get the number of terms

Mathematically, we have the formula for the sum of terms in an arithmetic sequence as

$sn = \frac{n}{2} (a + 1)$

a represents the first terms, and i represent the last term

$423 = \frac{n}{2} (15 + 79) \\ \\ 423 \times 2 = 94(n) \\ \\ 94n = 846 \\ \\ n = \frac{846}{94} \\ \\ n = 9$