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Permutations and Combinations

JEE Main 2025 (Online) 28th January Evening ShiftNumericalMedium📈 Topic in 16% papers+4
Ques. 1JEE Main 2025, 28 January (Evening Shift)

The number of natural numbers, between 212 and 999, such that the sum of their digits is 15, is .

Answer

64

Solution

Let the number be abc, 1 a 9, 0 b, c 9, b + c = 15 - a.

Number of pairs (b, c) with b + c = s: s + 1 if s 9, 19 - s if s 9.

a = 1 (s = 14): 5; a = 2 (s = 13): 6; a = 3 (s = 12): 7

a = 4 (s = 11): 8; a = 5 (s = 10): 9; a = 6 (s = 9): 10

a = 7 (s = 8): 9; a = 8 (s = 7): 8; a = 9 (s = 6): 7

Total from 100 to 999 = 69

Numbers ≤ 212 with digit sum 15: all 5 with a = 1 (159, 168, 177, 186, 195); for a = 2 the smallest is 249 > 212.

required number = 69 - 5 = 64

Answer: 64

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Ques. 2JEE Main 2026, 8 April (Evening Shift)

A person has three different bags and four different books. The number of ways, in which he can put these books in the bags so that no bag is empty, is :

  1. 18
  2. 36
  3. 39
  4. 72
Ques. 3JEE Main 2026, 6 April (Morning Shift)

The number of 4-letter words, with or without meaning, each consisting of two vowels and two consonants that can be formed from the letters of the word INCONSEQUENTIAL, without repeating any letter, is :

  1. 2670
  2. 2840
  3. 2920
  4. 3600
Ques. 4JEE Main 2026, 6 April (Evening Shift)

A building has ground floor and 10 more floors. Nine persons enter in a lift at the ground floor. The lift goes up to the 10th floor. The number of ways, in which any 4 persons exit at a floor and the remaining 5 persons exit at a different floor, if the lift does not stop at the first and the second floors, is equal to :

  1. 2184
  2. 3064
  3. 7056
  4. 11340
Ques. 5JEE Main 2026, 5 April (Morning Shift)

Two players A and B play a series of games of badminton. The player, who wins 5 games first, wins the series. Assuming that no game ends in a draw, the number of ways, in which player A wins the series is .

Ques. 6JEE Main 2026, 5 April (Evening Shift)

A box contains 5 blue, 6 yellow and 4 red balls. The number of ways, of drawing 8 balls containing at least two balls of each colour, is :

  1. 4100
  2. 4140
  3. 4230
  4. 4290
Ques. 7JEE Main 2026, 4 April (Morning Shift)

The number of ways, of forming a queue of 4 boys and 3 girls such that all the girls are not together, is:

  1. 5040
  2. 3050
  3. 3410
  4. 4320
Ques. 8JEE Main 2026, 4 April (Evening Shift)

Let A=\(a, b, c) : a, b, c are non-negative integers and a+b+2c=22\. Then n(A) is equal to :

  1. 121
  2. 124
  3. 144
  4. 169
Ques. 9JEE Main 2026, 2 April (Morning Shift)

The number of seven-digit numbers, that can be formed by using the digits 1, 2, 3, 5 and 7 such that each digit is used at least once, is :

  1. 15400
  2. 17800
  3. 16800
  4. 29400
Ques. 10JEE Main 2026, 2 April (Evening Shift)

Let pn denote the total number of triangles formed by joining the vertices of an n-side regular polygon. If pn+1-pn=66, then the sum of all distinct prime divisors of n is :

  1. 7
  2. 8
  3. 5
  4. 6
Ques. 11JEE Main 2026, 28 January (Morning Shift)

Let S = \1, 2, 3, 4, 5, 6, 7, 8, 9\. Let x be the number of 9-digit numbers formed using the digits of the set S such that only one digit is repeated and it is repeated exactly twice. Let y be the number of 9-digit numbers formed using the digits of the set S such that only two digits are repeated and each of these is repeated exactly twice. Then,

  1. 56x = 9y
  2. 21x = 4y
  3. 45x = 7y
  4. 29x = 5y

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