An important and exam oriented question from arithmetic progression chapter as it has been already asked in previous year paper in which we are to find which term of the AP 21, 18, 15,….is -81?

Book – RS Aggarwal, Class 10, Arithmetic Progression, chapter 5A, question no 14

AP :8,14,20,26...

a=8

d=14−8=6

Let Tn=T41+72

a+(n−1)d=a+40d+72

⇒a+(n−1)d−a−40d=72

⇒d(n−1−40)=72

⇒6(n−41)=72

⇒n−41=12

⇒n=12+41

∴n=53

Required term = 53

53th term of AP will be 72 more than its 41th term