logo

CuriousTab

CuriousTab

Discussion


Home Aptitude Permutation and Combination See What Others Are Saying!
  • Question
  • Suppose 7 students are staying in a hall in a hostel and they are allotted 7 beds. Among them, Parvin does not want a bed next to Anju because Anju snores. Then, in how many ways can you allot the beds?


  • Options
  • A. 2400
  • B. 6400
  • C. 3600
  • D. 7200

  • Correct Answer
  • 3600 

    Explanation

    Let the beds be numbered 1 to 7.

     

    Case 1 : Suppose Anju is allotted bed number 1. 

    Then, Parvin cannot be allotted bed number 2. 

    So Parvin can be allotted a bed in 5 ways. 

    After alloting a bed to Parvin, the remaining 5 students can be allotted beds in 5! ways.

    So, in this case the beds can be allotted in 5´5!ways = 600 ways.

     

    Case 2 : Anju is allotted bed number 7. 

    Then, Parvin cannot be allotted bed number 6 

    As in Case 1, the beds can be allotted in 600 ways.

     

    Case 3 : Anju is allotted one of the beds numbered 2,3,4,5 or 6. 

    Parvin cannot be allotted the beds on the right hand side and left hand side of Anju?s bed. For example, if Anju is allotted bed number 2, beds numbered 1 or 3 cannot be allotted to Parvin.

    Therefore, Parvin can be allotted a bed in 4 ways in all these cases.

    After allotting a bed to Parvin, the other 5 can be allotted a bed in 5! ways.

    Therefore, in each of these cases, the beds can be allotted in 4´ 5! = 480 ways. 

    The beds can be allotted in (2x 600 + 5 x 480)ways = (1200 + 2400)ways = 3600 ways


  • More questions

    • 1. 
      Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?

    • Options
    • A. 18 days
    • B. 21 days
    • C. 3 days
    • D. 6 days
    • Discuss
    • 2. 
      750.0003 ÷ 19.999 =?

    • Options
    • A. 49
    • B. 18
    • C. 22
    • D. 38
    • Discuss
    • 3. 
      105, 85, 60, 30, 0, - 45, - 90?

    • Options
    • A. 0
    • B. 85
    • C. -45
    • D. 60
    • Discuss
    • 4. 
      Let A = {1, 2, {3, 4}, 5}. Which of the following statements is true?

    • Options
    • A. {3, 4} ? A
    • B. {3, 4} ? A
    • C. 1 ? A
    • D. {1, 2, 5} ? A
    • Discuss
    • 5. 
      Two vessels A and B contains milk and water mixed in the ratio 5 : 3 and 2 : 3. When these mixtures are mixed to form a new mixture containing half milk and half water, they must be taken in the ratio ?

    • Options
    • A. 2 : 5
    • B. 3 : 5
    • C. 4 : 5
    • D. 7 : 3
    • Discuss
    • 6. 
      1, 2, 4, 8, 16, 32, 64, (...), 256?

    • Options
    • A. 148
    • B. 128
    • C. 154
    • D. 164
    • Discuss
    • 7. 
      A tree is 12 m tall and casts an an 8 m long shadow. At the same time, a flag pole caste a 100 m long shadow. How long is the flag pole?

    • Options
    • A. 150 m
    • B. 200 m
    • C. 125 m
    • D. 115 m
    • Discuss
    • 8. 
      8% of 96 =? of 1/25

    • Options
    • A. 19.2
    • B. 7.68
    • C. 1.92
    • D. None of these
    • Discuss
    • 9. A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?

    • Options
    • A. Rs. 35
    • B. Rs. 245
    • C. Rs. 350
    • D. Cannot be determined
    • E. None of these
    • Discuss
    • 10. 
      If the hands of a clock coincide in every 65 minutes (true time), in 24 hours the clock will gain:

    • Options
    • A. 10 10 minutes. 143
    • B. 9 12 minutes. 143
    • C. 11 12 minutes. 143
    • D. 12 10 minutes. 143
    • Discuss


    Comments

    There are no comments.

Enter a new Comment