Q. 75.0( 1 Vote )

# The first term an

Given, first term a = 1, last term l = 11 and Sn = 36.
Since, nth term an is given by :
an = a + (n - 1)d

Where,

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

11 = 1 + (n - 1)d
10 = (n -1)d … (i)

Since the sum of n terms is
Sn =  72 = n[ 2 + (n-1)d] …(ii)

From eq. (i) and (ii), we get,
72 = n[ 2 + 10]
72 = 12n
n = 6

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Arithmetic Progression- Don't miss these Questions56 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 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