Find the sum of the first 22 terms of an AP in which d = 7 and 22^nd term is 149

Solution:

Sum of the first n terms of an AP is given by Sₙ = n/2 [2a + (n - 1) d].

Here, a is the first term, d is the common difference and n is the number of terms.

Given,

• 22^nd term, l = a₂₂ = 149
• Common difference, d = 7

We know that nth term of AP, aₙ = a + (n - 1)d

a₂₂ = a + (22 - 1) d

149 = a + 21 × 7

149 = a + 147

a = 2

The sum of 22 terms can be found as follows.

Sₙ = n/2 [a + l]

= 22/2 (2 + 149)

= 11 × 151

= 1661

☛ Check: NCERT Solutions Class 10 Maths Chapter 5

Video Solution:

Find the sum of the first 22 terms of an AP in which d = 7 and 22^nd term is 149

Class 10 Maths NCERT Solutions Chapter 5 Exercise 5.3 Question 7

Summary:

The sum of the first 22 terms of an AP in which d = 7 and 22^nd term is 149 is 1661.

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