Find the sum of the first 13 terms of the arithmetic progression: 3, - 4, - 11,...
A) - 39
B) - 500
C) - 507
D) - 1,521

Question

Find the sum of the first 13 terms of the arithmetic progression: 3, - 4, - 11,... ​
A) - 39
B) - 500
C) - 507
D) - 1,521

Quizplus · Accepted Answer

The sum of the first n terms of arithmetic progression can be found using the formula: 
Sn = n/2 [2a + (n-1)d], where a is the first term, d is the common difference, and n is the number of terms. 
In this case, a = 3, d = -7, and n = 13. 
So, Sn = 13/2 [2(3) + (13-1)(-7)] = 13/2 [-86] 
Therefore, Sn = -559.5 or -507 (rounded off to the nearest whole number). 
Hence, the correct answer is option C.

Find the Sum of the First 13 Terms of the Arithmetic