envelopes

  1. M

    Question about envelopes

    Hello, I have a problem about envelopes. Please if someone can help me ?? Thank you. Compute the envelopes of the family of lines x1+a2x2-2a=0 (a ԑ R) in R2 and of the family of planes 2a1x1+2a2x2-x3+a12+a22=0 (a1, a2 ԑ R) in R3 . Draw pictures illustrating the geometric meaning...
  2. V

    the two envelopes problem. My take. I want to know opinions)

    The two envelopes paradox “You have two indistinguishable envelopes that each contain money. One contains twice as much as the other. You may pick one envelope and keep the money it contains. You pick at random, but before you open the envelope, you are offered the chance to take the other...
  3. N

    Letters and envelopes

    Suppose that you have 20 different letters and 10 distinctly addressed envelopes. The 20 letters consist of 10 pairs, where each pair belongs inside one of the 10 envelopes. Suppose that you place the 20 letters inside the 10 envelopes, two per envelope, but at random. What is the...
  4. H

    Putting letters into envelopes

    A secretary randomly put 10 letters in 10 envelope What is the probability that at least one letter was put in the correct envelope? I solved it as follows The probability of 0 letters in the correct envelope is 9/10 8/9.... = 9!/10! what is my mistake ?
  5. hungthinh92

    Envelopes and Paychecks Problems

    This is the first problem which I solved: You have 3 envelopes and 3 paychecks addressed to 3 different people. The paychecks are randomly inserted into the envelopes. What is the probability that at least one paycheck is inserted in the correct envelope. The answer is: 4/3!= 2/3 Then...
  6. F

    The two envelopes problem

    Introduction I came across the two envelopes problem a couple of weeks ago. I read the Wikipedia article, and this article by a mathematician named Keith Devlin, and for a while I felt like I understood the solution. I've been thinking about this a lot since then, and now I believe that those...