Here, first term is 21 and common difference is -3. Solving tn = a + (n – 1)d shows that -81 is the 35th term, and 0 is indeed the 8th term since n is a positive integer.
Which term of the AP : 21, 18, 15, … is – 81? Also, is 0 a term of this AP? Give reasons for your answer.
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For this AP, the first term is a = 21 and the common difference is d = 18 – 21 = -3.
The nth term formula is tn = a + (n – 1)d.
For tn = -81:
21 + (n – 1) x (-3) = -81
(n – 1) x (-3) = -102
n – 1 = 34, so n = 35. Thus, -81 is the 35th term.
For tn = 0:
21 + (n – 1) x (-3) = 0
(n – 1) x (-3) = -21
n – 1 = 7, so n = 8.
Since n is a natural number, 0 is the 8th term.
For more NCERT Solutions of Class 9 Ganita Manjari Chapter 8 Predicting What Comes Next: Exploring Sequences and Progressions Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/maths/ganita-manjari-chapter-8/