# (5 + 13 + 21 + + 181) =?A. 2476B. 2337C. 2219D. 2139

Here, first term = 5

Common difference = d = 13 - 5 = 8

Last term = l = 253

To find: number of terms in the Arithmetic series

So, nth term is given by:

an = a + (n - 1)d

181 = 5 + (n - 1) × 8

181 - 5 = 8n - 8

176 = 8n - 8

176 + 8 = 8n

8n = 184

n = 23

Thus there are 23 terms in the arithmetic series.

Sum of first n terms of an AP is

Sn = [2a + (n - 1)d]

Sum of 23 terms is given by:

S23 = [2(5) + (23 - 1)(8)]

= (23/2) × [10 + 176]

= (23/2) × 186

= 23 × 93

= 2139

Thus, sum of 23 terms of this Arithmetic series is 2139.

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Champ Quiz | Arithmetic Progression34 mins
Champ Quiz | Arithmetic Progression30 mins
Lets Check Your Knowledge in A.P.49 mins
Arithmetic progression: Previous Year NTSE Questions34 mins
Quiz on Arithmetic Progression Quiz32 mins
Arithmetic Progression Tricks and QUIZ37 mins
Quiz | Group of Questions on General Term of an A.P49 mins
Get to Know About Geometric Progression41 mins
NCERT | Solving Questions on Introduction of A.P42 mins
Become a Master of A.P. in 45 Minutes!!47 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses