WebQuestion If an AP has a = 1, a n = 20 and S n = 399, then find the value of n. Solution Compute the value of n: Formulae: The n th term of an AP is a n = a + n - 1 d and the sum of n terms of a series in an AP is S n = n 2 2 a + ( n - 1) d. Substitute a = 1, a n = 20 in the n th term of an AP formula. WebMar 11, 2024 · answered In an Ap, a=1, an=20, sn=399 then find n Advertisement Answer 3 people found it helpful pragyanrana31 Answer: Sn=n/2 (a+l) . . 399=n/2 (1+20) . . 399*2/21=n . . 19*2=n . . N=38 . . Hope this helps you . . Pls mark Brainliest answer! ️ Find Math textbook solutions? Class 6 Class 5 Class 4 Class 3 Class 2 Class 1 NCERT Class 9 …
In an AP if a = 1, an = 20 and Sn = 399, then n is (A) 19 (B) 21 (C) …
WebAnswer : Let the required numbers in A.P.are (a - d), a and (a + d). Sum of these numbers = (a - d) + a + (a + d) = 3a Product of these numbers = (a - d)× a × (a + d)=a (a 2 - d 2) But given, sum = 24 and product = 440 ∴ 3a = 24 a = 8 and a (a 2 - d 2) = 8 (64 - d 2) = 440 [ a = 8] Or, 64 - d 2 = 55 Or, d 2 = 64 - 55 => d 2 = 9 => d = ± 3 WebJan 23, 2024 · In an AP if a = 1, an = 20 and Sn = 399, then n is (A) 19 (B) 21 (C) 38 (D) 42. 2Pi classes. 36.7K subscribers. bins ccv
{Latest Edition} NCERT Exemplar Class 10 Maths Solutions Chapter …
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 WebIn an AP if a = 1, an = 20 and Sn = 399, then n is _____. CBSE English Medium Class 10. Question Papers 939. Textbook Solutions 33590. MCQ Online Mock Tests 12. Important … 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? bins ccs