Finding nth term

Chapter 5 Class 10 Arithmetic Progressions
Concept wise

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### Transcript

Ex 5.2, 8 An A.P. consists of 50 terms of which 3rd term is 12 and the last term is 106. Find the 29th term We know that an = a + (n – 1) d Given 3rd term is 12 a3 = a + (3 – 1) d 12 = a + 2d 12 – 2d = a a = 12 – 2d Given last term is 106 Last term = 50th term = a50 = 106 Now, a50 = a + (50 – 1) d 106 = a + 49 d 106 – 49d = a a = 106 – 49d From (1) and (2) 12 – 2d = 106 – 49d –2d + 49d = 106 – 12 47d = 94 d = 94/47 d = 2 Putting the value of d in (1) a = 12 – 2d a = 12 – 2 × 2 a = 12 – 4 a = 8 Now, We need to find 29th term i.e. a29 Now, an = a + (n – 1) d Putting values a29 = 8 + (29 – 1) × 2 = 8 + 28 × 2 = 8 + 56 = 64 Hence, 29th term = a29 = 64

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.