# How many terms of A.P -10, -7, -4, -1, ........ must be added to get the sum 104?

Given:
-10, -7, -4, -1, ........
Clearly,

a = -10, d = 3  2 × 104 = n[-20 + 3n – 3]

208 = n (3n – 23)
3n 2 – 23n - 208 = 0

3n 2 – 39n + 16n - 208 = 0
3n (n – 13) + 16 (n – 13) = 0
(n – 13) (3n + 16) = 0

n = 13, it cannot be a fraction
n = 13
Hence 13 terms must be added to get the sum of the A.P  104.

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  Quiz | Arithmetic Progression44 mins  NCERT | Fundamental Theorem Of Arithmetic45 mins  Lets Check Your Knowledge in A.P.49 mins  Smart Revision | Arithmetic Progression47 mins  Quiz on Arithmetic Progression Quiz32 mins  Get to Know About Geometric Progression41 mins  NCERT | Solving Questions on Introduction of A.P42 mins  Smart Revision | Imp. Qs. on Arithmetic Progression46 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 