NCERT Solutions for Class 10 Maths Chapter 5

Important NCERT Questions

Arithmetic Progression

NCERT Books for Session 2022-2023

CBSE Board and UP Board Others state Board

EXERCISE 5.4

Page No:115

Questions No:1

# Which term of the AP : 121, 117, 113, . . ., is its first negative term?

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Here, a = 121 and d = 117 – 121 = – 4.

Let, a_n be the first negative term of this AP.

⇒ a_n < 0

⇒ a + (n – 1)d < 0

⇒ 121 + (n -1)(-4) < 0

⇒ 121 – 4n + 4 < 0

⇒ 125 125/4

⇒ n > 31.25

⇒ n = 32

Hence, 32nd term of the AP: 121, 117, 113 … is its first negative term.