Q. 145.0( 2 Votes )

Which term of the A.P. 4, 9, 14, ... is 89? Also, find the sum 4 + 9 + 14 + + 89.

Answer :

Let an = 89


AP = 4, 9, 14, …89


Here, a = 4, d = 14 – 9 = 5


We know that


an = a + (n – 1)d


89 = 4 + (n – 1)5


85 = (n – 1)5


17 = n – 1


18 = n


So, 89 is the 18th term of the given AP


Now, we find the sum of 4 + 9 + 14 + … + 89


We know that,




S18 = 9[8 + 17 × 5]


S18 = 9[8 + 85]


S18 = 9 × 93


S18 = 837


Hence, the sum of the given AP is 837.


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
NCERT | Fundamental Theorem Of Arithmetic45 mins
Fundamental Theorem of Arithmetic- 143 mins
Quiz on Arithmetic Progression Quiz32 mins
Arithmetic progression: Previous Year NTSE Questions34 mins
Get to Know About Geometric Progression41 mins
NCERT | Solving Questions on Introduction of A.P42 mins
Arithmetic Progression Tricks and QUIZ37 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