Example 12 - Chapter 5 Class 10 Arithmetic Progressions

Last updated at April 16, 2024 by

Example 12 - If sum of first 14 terms of an AP is 1050 - Examples

Example 12 - Chapter 5 Class 10 Arithmetic Progressions - Part 2

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Example 12 If the sum of the first 14 terms of an AP is 1050 and its first term is 10, find the 20th term. Here, Sum of the first 14 terms of an AP is 1050. So, S14 = 1050 Also, a = 10 & n = 14 We know that Sum = 𝒏/𝟐[𝟐𝒂+(𝒏−𝟏)𝒅] Putting values 1050 = 14/2[2×(10)+(14−1)𝑑] 1050 = 7[20+13𝑑] 1050/7=20+13𝑑 150 = 20 + 13d 13d = 150 – 20 13d = 130 d = 10 We have to find 20th term We use the formula an = a + (n – 1) d Putting a = 10 , d = 10 , n = 20 a20 = 10 + (20 – 1) 10 a20 = 10 + (19 )×10 a20 = 10 + 190 a20 = 200

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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