Jump to content
BrainDen.com - Brain Teasers


  • Content count

  • Joined

  • Last visited

  • Days Won


Everything posted by bonanova

  1. Hi ammar97 and welcome to the Den. The first puzzle is a standard liar-truth teller puzzle. This is the most basic of them and has been posted here in the past. There are ways to make the answer more complicated and it's a great way to think logically to solve puzzles of this type. (Suppose one of the persons randomly tells the truth, and so on.) You can actually search the site, using keywords, to see if a puzzle has been posted already. (Click the Activity tab and choose Search.) The second puzzle is less well known, and the solution comes with nice "aha!" moment. The third puzzle belongs to a broad genre of bridge-crossing puzzles. I found yours very interesting. Easy to analyze but counter intuitive to solve. There are only a few possibilities, but the answer lies well hidden among them. Thanks again for posting these puzzles, and feel free to post others, that you either write yourself or find on the Web. But here's a hint: If a published puzzle comes with a solution, then instead of linking to it, you could give it here in your own words (without the solution.) That way we won't have access to the solution until someone here solves it. Thanks again.
  2. Probability of finding a three.

    Yikes! Really? It's 24 times more likely for a 3 to be drawn 5th than to be drawn 1st?
  3. 4 hats puzzle

    I like phaze's solution. I would add just a tweak, as described in the second spoiler. Recap: Tweak.
  4. Celebrity Interview

    You are on the right track.
  5. Mega Einstein Riddle

    It would be more fun if there were five of us in a room working on it together. I've been distracted by other things lately but still interested.
  6. 4 hats puzzle

    First thoughts (that are consistent with a better result than in the 3-person example):
  7. Who should do what

    I've brought this up with site management to have replies ordered chronologically. I think that's the order now. It's confusing otherwise.
  8. Descendants

    Yeah, that's it. I have an online tree now (ancestry.com) with a few thousand names. I get inquiries and "matches" almost daily from people who descended from an uncle's sister-in-law of an 8th-generaltion direct ancestor. Soon you realize how interconnected the human family is. The gene pool is constantly being stirred. Even if you could map the whole thing you'd need a lot of color coding to discern in individual's tree. We'd all be different colors simultaneously, and a lot of "branches" would be tied into knots. (Rednecks all... )
  9. Descendants

    I get that. I thought it was strange that the question was introduced with an "overpopulation" flavor. (Maybe it was just a red herring.) My comment badly implied that yours wasn't responsive to the question; I meant to opine that the introduction wasn't all that germane. There are a couple of "paradoxes" when one considers family trees and such. For example we all have two parents, four grandparents, eight GGPs, sixteen GGGPs, and so on. So how is an exponentially increasing heritage as we go back in time consistent with a growing population going forward? Was there an original, parenting "couple" N generations back? If so, how could they singly play all the roles of my 2N progenitors at that time? And, if two kids/family going forward gives a stable population, how can it also produce an exponential personal progeny? I found Mitochondrial Eve an interesting read.
  10. logic or trial&error?

    Brute force Has anyone found a constructive solution?
  11. Descendants

    "... for a thousand years. How many descendants would you have?" But we're not enumerating the world's population. We're quantifying the part of it that comprises your descendants. Two children, four grandchildren, ...
  12. logic or trial&error?

    Give it a try:
  13. Descendants

    Doesn't each birth increase the population? What if, miraculously, no one will die? But the question does not hinge on when/whether people will die. The question asks: how many descendants will you have?
  14. Who should do what

    @BMAD The three of us: you, I, and Logo, agree on the 5 4 1 5 3 = 18 assignment. I like your approach, where the solution can be constructed.
  15. Who should do what

    Can we see it?
  16. Probability of finding a three.

    A quick and dirty analysis
  17. Descendants

    First thought
  18. logic or trial&error?

    It might be solvable, iteratively. I once posted a puzzle, here or elsewhere, that went as follows: But in that puzzle information was added as the constraints were iteratively applied. Here it seems it must all be determined in one shot. So maybe that's not possible.
  19. Hitting a double

    "Determine the rate of change to second base once the runner reaches halfway to first base." Determine the time rate of change of the distance between the runner and 2nd base when the runner is halfway between home plate and first base, running at 24 ft/sec on a path that is a straight line from home plate to first base. If these two statements ask for the same information, then
  20. Who should do what

    Logophobic has it.
  21. Hitting a double

    Of his position? Of his velocity? Most runners going to 2nd base will swing wide to round out the corner and keep a constant speed.
  22. Making a spiral

    Agreed. Quite a bit off. Upon further review my guess (of a cosine relationship of line angle to wall angle) was wrong.