Find the n th partial sum of the arithmetic sequence. 8 , 13 , 18 , 23 , 28 , … , n = 12 8,13,18,23,28 , \ldots , n = 12 8 , 13 , 18 , 23 , 28 , … , n = 12 A) 390B) 438C) 426D) 354E) 402

Question

Find the n th partial sum of the arithmetic sequence.   8 , 13 , 18 , 23 , 28 , … , n = 12 8,13,18,23,28 , \ldots , n = 12 8 , 13 , 18 , 23 , 28 , … , n = 12 A)  390B)  438C)  426D)  354E)  402

Sakiko Harada · Accepted Answer

Final Answer : C, Explanation :   The common difference between consecutive terms is $13-8=5$. Therefore, the $n$th term is equal to $8 + 5(n-1)$. To find the sum of the first 12 terms, we use the formula for the sum of an arithmetic series: S 12 = 12 2 ( 8 + ( 8 + 5 ( 12 − 1 ) ) ) = 6 ( 8 + 59 ) = 426 S_{12}=\frac{12}{2}(8+(8+5(12-1))) = 6(8+59) = 426 S 12 ​ = 2 12 ​ ( 8 + ( 8 + 5 ( 12 − 1 ))) = 6 ( 8 + 59 ) = 426 Thus, the correct choice is $\boxed{	extbf{(C)}}$.

Find the n th partial sum of the arithmetic sequence. $\ldots , n = 12$

A) 390
B) 438
C) 426
D) 354
E) 402

Definitions

Learning Objectives

Learning Objectives

Related questions

Find the n th partial sum of the arithmetic sequence. 8,13,18,23,28,…,n=128,13,18,23,28 , \ldots , n = 128,13,18,23,28,…,n=12 A) 390B) 438C) 426D) 354E) 402

Definitions

Learning Objectives

Learning Objectives

Related questions

Find the n th partial sum of the arithmetic sequence. $\ldots , n = 12$

A) 390
B) 438
C) 426
D) 354
E) 402