Answer :

General nth term an is given as:
an = a + (n - 1)d … (i)


Where,


a = First term of AP
d = Common difference of AP
and no of terms is ‘n’



and an = 3 + 4n
an = (7-4) + 4n
an = 7 + 4n – 4
an = 7 + 4(n – 1)
an = 7+ (n – 1)× 4 …(ii)


On comparing eq. (i) and (ii), we get,
a = 7 and d = 4


Here first term is 7 and common difference is 4.
Since the sum of n terms is
Sn =


Where,


a = First term of AP
d = Common difference of AP
and no of terms is ‘n’



So sum of first 25 terms S25
= 12.5 × [ 14 + 24×4]
= 12.5 × [ 14 + 96]
= 12.5 × 110
= 1375


Hence, Sum of first 25 terms is 1375.


Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Sum of n Terms of APSum of n Terms of APSum of n Terms of AP56 mins
Arithmetic Progression and 'nth' Term of APArithmetic Progression and 'nth' Term of APArithmetic Progression and 'nth' Term of AP55 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
caricature
view all courses
RELATED QUESTIONS :

A sum of 280 is tRajasthan Board Mathematics

If the sum of theRajasthan Board Mathematics

Find the sum of aRajasthan Board Mathematics

Find the sum of tRajasthan Board Mathematics

Find the sum of tRajasthan Board Mathematics

Find the sum of tRajasthan Board Mathematics

Find the sum of tRajasthan Board Mathematics

Find the number oRajasthan Board Mathematics

The first term anRajasthan Board Mathematics

If the sum of n tRajasthan Board Mathematics