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11 votes
11 votes
Determine the number of terms n :

a 1 = 15, a n = 79, S n = 423

User TommyVee
by
2.7k points

1 Answer

24 votes
24 votes

Answer:

The number of terms in the sequence is 9

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 = (n)/(2) (a + 1)

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


423 = (n)/(2) (15 + 79) \\ \\ 423 * 2 = 94(n) \\ \\ 94n = 846 \\ \\ n = (846)/(94) \\ \\ n = 9

User Reyno
by
3.3k points
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