Example 12 - Chapter 5 Class 10 Arithmetic Progressions (Term 2)
Last updated at March 19, 2021 by Teachoo
Examples
Example 1
Example 2 Important
Example 3
Example 4 Important
Example 5
Example 6 Important
Example 7
Example 8 Important
Example 9
Example 10
Example 11
Example 12 You are here
Example 13 Important
Example 14 (i)
Example 14 (ii)
Example 15 Important
Example 16 Important Deleted for CBSE Board 2022 Exams
Chapter 5 Class 10 Arithmetic Progressions (Term 2)
Serial order wise
Transcript
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
