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Permutations and Combinations · Question 35

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

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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2

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
JEE Main 2026 (Online) 8th April Evening Shift
3

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
JEE Main 2026 (Online) 6th April Morning Shift
4

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
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5

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 .

JEE Main 2026 (Online) 5th April Morning Shift
6

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
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7

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
JEE Main 2026 (Online) 4th April Morning Shift
8

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
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9

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
JEE Main 2026 (Online) 2nd April Morning Shift
10

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
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11

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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