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Permutations and Combinations

JEE Main 2024 (Online) 8th April Morning ShiftNumericalEasy📈 Topic in 10% papers+4
Ques. 1JEE 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 .

Answer

36

Solution

A number is divisible by 3 only when its digit sum is divisible by 3, so we pick the digit sets whose sum is not a multiple of 3.

Such sets from \2, 3, 4, 5, 7\ (digit sum): \2, 3, 5\ (10), \2, 4, 5\ (11), \2, 4, 7\ (13), \2, 5, 7\ (14), \3, 4, 7\ (14), \4, 5, 7\ (16), i.e. 6 sets

(the remaining sets \2, 3, 4\, \2, 3, 7\, \3, 4, 5\, \3, 5, 7\ have sums 9, 12, 12, 15, so they are left out)

Since digits are not repeated, each set gives 3! = 6 numbers.

Required number = 6 6 = 36

Answer: 36

Keep practising — Permutations and Combinations

Ques. 2JEE 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. 3JEE 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
Ques. 4JEE Main 2024, 6 April (Evening Shift)

If all the words with or without meaning made using all the letters of the word "NAGPUR" are arranged as in a dictionary, then the word at 315th position in this arrangement is :

  1. NRAPUG
  2. NRAGUP
  3. NRAPGU
  4. NRAGPU
Ques. 5JEE Main 2024, 6 April (Evening Shift)

Let 0 r n. If n+1Cr+1 : nCr : n-1Cr-1 = 55 : 35 : 21, then 2n + 5r is equal to :

  1. 62
  2. 60
  3. 55
  4. 50
Ques. 6JEE Main 2024, 5 April (Morning Shift)

The number of ways of getting a sum 16 on throwing a dice four times is .

Ques. 7JEE Main 2024, 5 April (Evening Shift)

Let the set S = \2, 4, 8, 16, , 512\ be partitioned into 3 sets A, B, C with equal number of elements such that A B C = S and A B = B C = A C = . The maximum number of such possible partitions of S is equal to:

  1. 1640
  2. 1520
  3. 1710
  4. 1680
Ques. 8JEE Main 2024, 5 April (Evening Shift)

60 words can be made using all the letters of the word BHBJO, with or without meaning. If these words are written as in a dictionary, then the 50th word is:

  1. OBBJH
  2. HBBJO
  3. OBBHJ
  4. JBBOH
Ques. 9JEE Main 2024, 4 April (Morning Shift)

There are 5 points P1, P2, P3, P4, P5 on the side AB, excluding A and B, of a triangle ABC. Similarly there are 6 points P6, P7, , P11 on the side BC and 7 points P12, P13, , P18 on the side CA of the triangle. The number of triangles, that can be formed using the points P1, P2, , P18 as vertices, is:

  1. 751
  2. 776
  3. 796
  4. 771
Ques. 10JEE Main 2024, 4 April (Evening Shift)

There are 4 men and 5 women in Group A, and 5 men and 4 women in Group B. If 4 persons are selected from each group, then the number of ways of selecting 4 men and 4 women is .

Ques. 11JEE Main 2024, 1 February (Morning Shift)

If n is the number of ways five different employees can sit into four indistinguishable offices where any office may have any number of persons including zero, then n is equal to :

  1. 47
  2. 53
  3. 51
  4. 43

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