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Home Aptitude Permutation and Combination Comments

  • Question
  • In how many different ways can four books A, B, C and D be arranged one above another in a vertical order such that the books A and B are never in continuous position?


  • Options
  • A. 9
  • B. 12
  • C. 14
  • D. 18

  • Correct Answer
  • 12 

    Explanation

    The number of arrangement in which A and B are not together
    = Total number of arrangement - Number of arrangement in which A and B are together
    = 4! - 3! x 2! = 24 - 12 = 12


  • Permutation and Combination problems


    Search Results


    • 1. 
      A man has 9 friends, 4 boys and 5 girls. In how many ways can he invite them, if there have to be exactly 3 girls in the invitees?

    • Options
    • A. 320
    • B. 160
    • C. 80
    • D. 200
    • Discuss
    • 2. 
      A department had 8 male and female employees each. A project team involving 3 male and 3 female members needs to be chosen from the department employees. How many different projects teams can be chosen?

    • Options
    • A. 112896
    • B. 3136
    • C. 720
    • D. 112
    • Discuss
    • 3. 
      Two series of a question booklet for an aptitude test are to be given to twelve students. In how many ways can the students be placed in two rows of six each, so that there should be no identical series side by side and that the students sitting one behind the other should have the same series?

    • Options
    • A. 2 x 12C6 x (6!)2
    • B. 6! x 6!
    • C. 7! x 7!
    • D. None of these
    • Discuss
    • 4. 
      Find the number of different ways of forming a committee consisting of 3 men and 3 women from 6 men and 5 women.?

    • Options
    • A. 30
    • B. 20
    • C. 10
    • D. 25
    • Discuss
    • 5. 
      Find the number of ways of preparing a chain with 5 different coloured beads?

    • Options
    • A. 18
    • B. 24
    • C. 12
    • D. 30
    • Discuss
    • 6. 
      Boxes numbered 1, 2, 3, 4 and 5 are kept in a row and they are to be filled with either a red or a blue ball such that no two adjacent boxes can be filled with blue balls Then, how different arrangements are possible, given that all balls of a given colour are exactly identical in all respects?

    • Options
    • A. 8
    • B. 10
    • C. 15
    • D. 22
    • Discuss
    • 7. 
      A child has four pockets and three marbles. In how many ways, the child can put the marbles in the pockets?

    • Options
    • A. 12
    • B. 64
    • C. 256
    • D. 60
    • Discuss
    • 8. 
      In how many ways, can the letters of the word 'ASSASSINATION' be arranged, so that all the S are together?

    • Options
    • A. 10!
    • B. 14! (4!)
    • C. 151200
    • D. 3628800
    • Discuss
    • 9. 
      Find the number of ways, in which 12 different beads can be arranged to form a necklace .

    • Options
    • A. 11 !/2
    • B. 10 !/2
    • C. 12 !/2
    • D. Couldn't be determined
    • Discuss
    • 10. 
      20 persons were invited to a party. In how many ways, they and the host can be seated at a circular table?

    • Options
    • A. 18 !
    • B. 19 !
    • C. 20 !
    • D. Couldn't be determined
    • Discuss


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