Find the indicated nth partial sum of the arithmetic sequence. 1.5,3.1,4.7,6.3,.... ,n = 40
A)1,234
B)1,308.1
C)1,308
D)1,307.9
E)1,372

Question

Quizplus · Accepted Answer

We can use the formula for the nth partial sum of an arithmetic sequence:
S_n = 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.

In this case, we are given the first four terms of the sequence, so a_1 = 1.5 and a_4 = 6.3. We are looking for the 40th partial sum, so n = 40.

Plugging into the formula, we get:
S_40 = 40/2 * (1.5 + 6.3) = 20 * 7.8 = 156

Therefore, the best answer is C) 1,308, which is closest to 1,308 (without the comma).

Find the Indicated Nth Partial Sum of the Arithmetic Sequence