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Permutations and Combinations

JEE Main 2025 (Online) 24th January Morning ShiftNumericalHard📈 Topic in 21% papers+4
Ques. 1JEE Main 2025, 24 January (Morning Shift)

Let S=\p1,p2 ,p10\ be the set of first ten prime numbers. Let A=S P, where P is the set of all possible products of distinct elements of S. Then the number of all ordered pairs (x,y), x S, y A, such that x divides y, is .

Answer

5120

Solution

Each y A is a product of a non-empty subset of the 10 primes (different subsets give different numbers).

pi y pi is in the subset; the other 9 primes are free: 29=512 choices

pairs =10 512=5120

Answer: 5120

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Ques. 2JEE Main 2025, 24 January (Morning Shift)

The number of 3-digit numbers, that are divisible by 2 and 3, but not divisible by 4 and 9, is .

Ques. 3JEE Main 2025, 24 January (Evening Shift)

Group A consists of 7 boys and 3 girls, while group B consists of 6 boys and 5 girls. The number of ways, 4 boys and 4 girls can be invited for a picnic if 5 of them must be from group A and the remaining 3 from group B, is equal to :

  1. 8925
  2. 9100
  3. 8575
  4. 8750
Ques. 4JEE Main 2025, 23 January (Morning Shift)

The number of words, which can be formed using all the letters of the word "DAUGHTER", so that all the vowels never come together, is :

  1. 34000
  2. 37000
  3. 35000
  4. 36000
Ques. 5JEE Main 2025, 23 January (Evening Shift)

The number of ways, 5 boys and 4 girls can sit in a row so that either all the boys sit together or no two boys sit together, is .

Ques. 6JEE Main 2025, 22 January (Morning Shift)

From all the English alphabets, five letters are chosen and are arranged in alphabetical order. The total number of ways, in which the middle letter is ' M ', is :

  1. 6084
  2. 5148
  3. 14950
  4. 4356
Ques. 7JEE Main 2025, 22 January (Evening Shift)

In a group of 3 girls and 4 boys, there are two boys B1 and B2. The number of ways, in which these girls and boys can stand in a queue such that all the girls stand together, all the boys stand together, but B1 and B2 are not adjacent to each other, is :

  1. 120
  2. 96
  3. 72
  4. 144
Ques. 8JEE Main 2024, 9 April (Evening Shift)

The number of integers, between 100 and 1000 having the sum of their digits equal to 14, is .

Ques. 9JEE Main 2024, 8 April (Morning Shift)

The number of 3-digit numbers, formed using the digits 2, 3, 4, 5 and 7, when the repetition of digits is not allowed, and which are not divisible by 3 , is equal to .

Ques. 10JEE Main 2024, 8 April (Evening Shift)

The number of ways five alphabets can be chosen from the alphabets of the word MATHEMATICS, where the chosen alphabets are not necessarily distinct, is equal to:

  1. 179
  2. 177
  3. 175
  4. 181
Ques. 11JEE Main 2024, 6 April (Morning Shift)

The number of triangles whose vertices are at the vertices of a regular octagon but none of whose sides is a side of the octagon is

  1. 56
  2. 16
  3. 24
  4. 48

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