Which term of the Arithmetic Progression (A.P.) 4, 9, 14, 19, … is 109?

Question

Question

This question was previously asked in

Bihar STET Paper I: Mathematics (Held In 2019 - Shift 1)

Answer 1

Given:

Last Term = a_n = 109

Concept used:

a_n = a + (n - 1)d

a_n = nth term

a = first term

d = difference between two terms of AP

Calculation:

In the given AP,

a = 4

d = 9 - 4 = 5

⇒ 109 = 4 + (n - 1)5

⇒ 109 - 4 = 5n - 5

⇒ 105 + 5 = 5n

⇒ 5n = 110

⇒ n = 22

∴ 109 is 22nd term of AP.

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