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Permutations and Combinations

JEE Main 2025 (Online) 24th January Morning ShiftNumericalHard📈 Topic in 16% 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

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