Ex 5.3, 6 - The first and last term of AP are 17 and 350 - Determining AP and finding sum

  1. Chapter 5 Class 10 Arithmetic Progressions
  2. Serial order wise
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Ex 5.3 ,6 The first and the last term of an AP are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum? Given a = 17 , l = 350, d = 9 We need to find how many terms i.e. n and their sum i.e. Sn From (1) and (2) 367× 𝑛/2 = 𝑛/2 (25 + 9n) 367 = 25 + 9n 367 – 25 = 9n 342 = 9n 342/9 = n 38 = n n = 38 Now, we need to find sum Putting value of n in (1) Sum = 367 × 𝑛/2 = 367 × 38/2 = 367 × 19 = 6973

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