Example 15 - Chapter 5 Class 10 Arithmetic Progressions (Term 2)
Last updated at Aug. 3, 2021 by Teachoo
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Chapter 5 Class 10 Arithmetic Progressions (Term 2)
Serial order wise
Transcript
Example 15 Find the sum of first 24 terms of the list of numbers whose nth term is given by an = 3 + 2n Given an = 3 + 2n Now, 1st term = a1 = 3 + 2 (1) a = 3 + 2 a = 5 2nd term = a2 = 3 + 2(2) = 3 + 4 = 7 3rd term = a3 = 3 + 2 (3) = 3 + 6 = 9 4th term = a4 = 3 + 2 (4) = 3 + 8 = 11 So, the series is 5, 7, 9, 11 ……… Since Difference between consecutive terms is same, So, it is an AP We need to find sum of first 24 terms So, n = 24, a = 5 d = 7 – 5 = 2 Putting these values in formula Sum = 𝑛/2[2𝑎+(𝑛−1)𝑑] = 24/2[2 × 5+(24−1)2] = 12 [10+(23)(2)] = 12 [10+46] = 12 × 56 = 672 Hence, Sum of 24th terms is 672
