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Ex 5.3, 5 - Chapter 5 Class 10 Arithmetic Progressions
Last updated at August 17, 2026 by Teachoo
Finding number of terms given s
Chapter 5 Class 10 Arithmetic Progressions
Concept wise
- Checking if AP or not and finding a, d
- Finding nth term
- Finding n
- Finding AP
- Finding nth term from end
- Divisible/ multiples
- Statement questions - nth term
- Finding sum of n terms
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Finding number of terms given s
- Given nth term finding s
- Statement questions - Sum of n terms
- Determining AP and finding sum
Transcript
Ex 5.3, 5 The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference. Given a = 5 , l = 45 & Sn = Sum = 400 Since last term is given, we can use formula Sn = ๐/๐ (a + l) Putting values in formula 400 = ๐/2 (5 + 45) 400 = ๐/2 ร 50 (400 ร 2)/50 = n 8 ร 2 = n 16 = n n = 16 So, Number of terms = 16 Finding d For d, we use the formula Sn = ๐/๐ (2a + n โ 1) d) Putting Sn = 400, n = 16, a = 5 400 = 16/2 (2 ร 5 + (16 โ 1)ร d) 400 = 8 ร (10 + 15d) 400/8 = 10 + 15d 50 = 10 + 15d 50 โ 10 = 15d 40 = 15d 40/15 = d 8/3 = d d = ๐/๐
