Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Trending News

Promoted
Mwilkey
Lv 4
Mwilkey asked in Education & ReferenceHomework Help · 8 years ago

How many ways can you place 4 cards into 4 boxes?

Four cards labeled A, B, C, and D are randomly placed in four boxes labeled A, B, C, and D.

Count the number of elements in the event that no box contains a card with the same letter as the box.

2 Answers

Relevance
  • J. J..
    Lv 7
    8 years ago
    Favorite Answer

    I know that the answer is 9 (just by working out the sample space) but I can't think how to work it out mathematically.

    Box A Box B Box C Box D

    ------------------------------------

    B...........A.........D.........C

    B...........C.........D.........A

    B...........D.........A.........C

    C...........A.........D.........B

    C...........D.........A.........B

    C...........D.........B.........A

    D...........A.........B.........C

    D...........C.........A.........B

    D...........C.........B.........A

    I shall look with interest to see if anyone can work it out mathematically!

  • Anonymous
    5 years ago

    (n-1)!

Still have questions? Get your answers by asking now.