Ex 5.2, 5 - Chapter 5 Class 10 Arithmetic Progressions - Part 3

Ex 5.2, 5 - Chapter 5 Class 10 Arithmetic Progressions - Part 4

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Ex 5.2, 5 Find the number of terms in the following AP (ii) 18, 151/2, 13,……….,-47 18, 15 1/2 , 13, … 47 Here, an = – 47 a = 18 d = 15 1/2 – 18 = (15 × 2 + 1)/2 – 18 = 31/2 – 18 = (31 − 18 × 2)/2 = (31− 36)/2 = (−5)/2 We need to find n Putting values in formula an = a + (n – 1) d –47 = 18 + (n – 1) × ((−5)/2) –65 = (n – 1) × ((− 5)/2) (−65 × 2)/(−5) = (n – 1) 26 = n – 1 n – 1 = 26 n = 26 + 1 n = 27 Hence the number of terms in the given AP is 27

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo