Probability

Written on 12:22 pm by Vja Students

Ten seniors who share a house, decide to exchange graduation presents. Each of them put their name into a hat, mix the name cards thoroughly & draws a card out at random. What is the probability that none of the 10 people draws his or her own name ?

Ans: (9!/10!)

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3 Comments

  1. mak | 1 March 2008 at 10:31 am

    probablity is 0.1

     
  2. Unknown | 2 March 2008 at 9:05 pm

    1 / 10

     
  3. Anonymous | 30 March 2008 at 3:24 pm

    This question is incomplete. There can we several answers based on the sequence of people drawing names:

    case 1:
    1) First person draws a name. Probability that its not his is 9/10.
    2) The person whose name is drawn in the first case draws a name. Probability that its not his is 1.
    3) And similarly.
    This gives the probability as 9/10.

    case 2 (Matches with your answer):
    1) First person's draw, probability = 9/10.
    2) One of the people whose name is not already drawn draws the next card. Probability = 8/9.
    3) So on, similarly.
    This gives 9!/10! as you answered.

    There will be several answers based on whether the name of the person drawing the card is already drawn or not. Hence this question is incomplete.

     

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