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Sequences and Series

JEE Main 2025 (Online) 4th April Evening ShiftMCQMedium📈 Topic in 24% papers+4−1
Ques. 1JEE Main 2025, 4 April (Evening Shift)

If the sum of the first 20 terms of the series 4 14 + 3 12 + 14 + 4 24 + 3 22 + 24 + 4 34 + 3 32 + 34 + 4 44 + 3 42 + 44 + is mn, where m and n are coprime, then m + n is equal to :

  1. 423
  2. 421
  3. 422
  4. 420

Answer

(2) 421

Solution

Tr = 4rr4 + 3r2 + 4

r4 + 3r2 + 4 = (r2 + 2)2 - r2 = (r2 - r + 2)(r2 + r + 2)

4r = 2 [(r2 + r + 2) - (r2 - r + 2) ]

Tr = 2 [ 1r2 - r + 2 - 1r2 + r + 2 ]

(r + 1)2 - (r + 1) + 2 = r2 + r + 2, the terms cancel in pairs (telescoping):

S20 = 2 [ 11 - 1 + 2 - 1400 + 20 + 2 ] = 2 [ 12 - 1422 ]

= 1 - 1211 = 210211

m = 210, n = 211 m + n = 421

Answer: (2)

Keep practising — Sequences and Series

Ques. 2JEE Main 2025, 4 April (Evening Shift)

Consider two sets A and B, each containing three numbers in A.P. Let the sum and the product of the elements of A be 36 and p respectively and the sum and the product of the elements of B be 36 and q respectively. Let d and D be the common differences of A.P.'s in A and B respectively such that D=d+3, d>0. If p+qp-q= 195, then p-q is equal to

  1. 540
  2. 450
  3. 600
  4. 630
Ques. 3JEE Main 2025, 3 April (Morning Shift)

Let a1, a2, a3, be a G.P. of increasing positive numbers. If a3 a5 = 729 and a2 + a4 = 1114, then 24(a1 + a2 + a3) is equal to

  1. 128
  2. 129
  3. 131
  4. 130
Ques. 4JEE Main 2025, 3 April (Morning Shift)

The sum 1 + 3 + 11 + 25 + 45 + 71 + upto 20 terms, is equal to

  1. 7240
  2. 8124
  3. 7130
  4. 6982
Ques. 5JEE Main 2025, 3 April (Evening Shift)

The sum 1 + 1 + 32! + 1 + 3 + 53! + 1 + 3 + 5 + 74! + up to terms, is equal to

  1. 3e
  2. 2e
  3. 4e
  4. 6e
Ques. 6JEE Main 2025, 2 April (Morning Shift)

Let a1, a2, a3, be in an A.P. such that k=112 a2k-1 = - 725a1, a1 0. If k=1n ak = 0, then n is :

  1. 18
  2. 17
  3. 11
  4. 10
Ques. 7JEE Main 2025, 2 April (Evening Shift)

The number of terms of an A.P. is even; the sum of all the odd terms is 24, the sum of all the even terms is 30 and the last term exceeds the first by 212. Then the number of terms which are integers in the A.P. is :

  1. 6
  2. 4
  3. 8
  4. 10
Ques. 8JEE Main 2025, 2 April (Evening Shift)

If the sum of the first 10 terms of the series 4 11 + 4 14 + 4 21 + 4 24 + 4 31 + 4 34 + is mn, where (m, n) = 1, then m + n is equal to .

Ques. 9JEE Main 2025, 29 January (Morning Shift)

Consider an A. P. of positive integers, whose sum of the first three terms is 54 and the sum of the first twenty terms lies between 1600 and 1800. Then its 11th term is :

  1. 108
  2. 90
  3. 122
  4. 84
Ques. 10JEE Main 2025, 29 January (Morning Shift)

The value of n ( k=1n k3 + 6k2 + 11k + 5(k+3)! ) is :

  1. 5/3
  2. 2
  3. 4/3
  4. 7/3
Ques. 11JEE Main 2025, 29 January (Evening Shift)

Let a1,a2, ,a2024 be an Arithmetic Progression such that a1+(a5+a10+a15+ +a2020)+a2024=2233. Then a1+a2+a3+ +a2024 is equal to .

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