# Ex 5.3, 7 - Chapter 5 Class 10 Arithmetic Progressions

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Ex 5.3 ,7 Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149. Given 22nd term = 149 We know that an = a + (n – 1) d Here, n = 22 , d = 7 , an = 149 Putting values in formula an = a + (n – 1) d 149 = a + (22 – 1) × 7 149 = a + 21 × 7 149 = a + 147 149 – 147 = a 2 = a a = 2 Now, we need to find sum of first 22 terms And we are given a22 = 149 So, last term = l = 149 We use the formula Sn = 𝑛/2 [ a + l ] Putting values = 22/2 [2 + 149] = 11 ×151 = 1661 Hence, Sum of first 22 terms is 1661,

Chapter 5 Class 10 Arithmetic Progressions

Serial order wise

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.