WebSolution Given: First term ( a) = a 1 = 1 n th term = a n = 20 Sum of n terms = S n = 399 Now, a n = a + n - 1 d ⇒ 20 = 1 + n - 1 d ⇒ n - 1 d = 20 - 1 ⇒ n - 1 d = 19... 1 S n = n 2 2 a + n - 1 d ⇒ 399 = n 2 2 1 + 19 From 1 ⇒ 399 = n 2 21 ⇒ 798 = 21 n ⇒ n = 798 21 ⇒ n = 38 Hence, the value of n is 38. Suggest Corrections 0 Similar questions Q. WebFeb 27, 2012 · In an AP if a=1, an= 20 and sn =399 then n is a) 13 b) 38 c) 21 d)19 - Maths - Arithmetic Progressions
In an AP, if a = 1, an = 20 and Sn = 399, then n is equal to …
WebBesides giving the explanation of In an A.P. if a=1,An=20 and Sn=399, then find the value of n.?, a detailed solution for In an A.P. if a=1,An=20 and Sn=399, then find the value of n.? has been provided alongside types of In an A.P. if a=1,An=20 and Sn=399, then find the value of n.? theory, EduRev gives you an ample number of questions to … WebIf in an AP a = 1, t n = 20 and Sn = 399 then n is (a) 19 (b) 21 (c) 38 (d) 42 Report 497 Share Follow Answer peter Reputation: 2.6K University of Lagos, Nigeria 30 July 2024 Comments 1 answer (s) ADVERTISEMENT - CONTINUE BELOW judziy Reputation: 3.0K University of Benin, Nigeria 30 July 2024 1 little buddy heater propane tank adapter
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WebIf an A.P. has a = 1, t n = 20 and s n = 399, then value of n is : A. 20 B. 32 C. 38 D. 40 Answer: Option C Solution (By Examveda Team) S n = 1 2 ( a + l) × n ⇒ 399 = ( 1 + 20) × n 2 ⇒ 399 × 2 = 21 × n ⇒ n = 399 × 2 21 ⇒ n = 19 × 2 ⇒ n = 38 Join The Discussion Related Questions on Progressions How many terms are there in 20, 25, 30 . . . . . . 140? WebIn an AP, if a = 1, an = 20 and Sn = 399, then n is equal to (a) 19 (b) 21 (c) 38 (d) 42 Solution: Question 18: The sum of first five multiples of 3 is (a) 45 (b) 55 (c) 65 (d) 75 Solution: (a) The first five multiples of 3 are 3, 6, 9,12 and 15. Here, first term, a = 3, common difference, d = 6-3 = 3 and number of terms, n = 5 WebFeb 11, 2013 · if an ap a=1 ,an=20,sn= 399 then n is Asked by anish mishra 11 Feb, 2013, 02:45: PM Expert Answer Sn=399 => n/2 (a + an) = 399 => n/2 ( 1 + 20) = 399 =>n/2 (21) = 399 => n = 399 X 2/21 => n= 38 Answered by 11 Feb, 2013, 05:49: PM Application Videos This video explains the concept of Arithmetic Progression, Solving Linear E... little buddy heater filter