Question 56. Let there be an A.P. with first term a and common difference d. If an denotes its nth term and Sn is the sum of first n terms, then find:(viii) S22, if d = 22 and a22 = 149

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deepaksoniGuru

Asked: July 1, 20212021-07-01T08:05:28+05:30 2021-07-01T08:05:28+05:30In: CBSE

This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6

In this question we have been given that there be an A.P.

first term a and common difference d.

Also, If an denotes its nth term and Sn is the sum of first n terms,

Now we have to find S22, if d = 22 and a22 = 149

CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 56(viii)

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AAREKH · Answer 1 · 2021-07-01T10:04:24+05:30

AAREKH Guru

We know, a₂₂ = a + 21d = 149 . . . . (1)

On putting d = 22 (given) in eq(1), we get

=> a + 21(22) = 149

=> a = 149 – 462

=> a = –313

We know, S₂₂ = 22[a + a₂₂] / 2

= 22[–313 + 149] / 2

= 11[164]

= 1804

Hence, the value of sum is 1804.