Jump to Last Post 1-27 of 27 discussions (29 posts)
  1. profile image48
    meg505posted 15 years ago

    A group of four people has to cross a bridge .It is dark, and they have to light the path with a flashlight . No more than two people can cross the bridge simultaneously , and the group has only one flashlight . It takes  different time for the people in the group to cross the bridge . Annie crosses the bridge in 1 minute, Bob crosses the bridge in 2 minutes, Cristy crosses the bridge in 5 minutes, Dorothy crosses the bride in 10 minutes. How can the group cross the bridge in 17 minutes?

    1. guidebaba profile image57
      guidebabaposted 14 years agoin reply to this

      Found the Answer: HERE tongue

  2. profile image49
    yen reyesposted 15 years ago

    The group will left Annie behind?

  3. caspar profile image60
    casparposted 15 years ago

    I think Dorothy is the one who should be left behind.  She's a liability. big_smile

  4. livelonger profile image90
    livelongerposted 15 years ago

    Bob seems strong - can't he give Dorothy a piggyback ride?

  5. livelonger profile image90
    livelongerposted 15 years ago


    This is my solution:
    Annie & Bob cross; Bob stays, Annie returns. (total 3 minutes)
    Cristy & Dorothy cross; they give the flashlight to Bob & he returns (total 12 mins)
    Annie & Bob cross (2 mins)
    = 17 minutes!

  6. Robin profile image90
    Robinposted 15 years ago

    I think you're right, Livelonger.  But, it isn't stated that they need to hold the flashlight.  What if they just laid the flashlight down at the head of the bridge to light it up, then everyone could easily cross without a problem.  Total time:   15 minutes or less depending on the pairings.  wink

  7. livelonger profile image90
    livelongerposted 15 years ago

    Your solution is a lot more clever, Robin! wink

  8. hedgeek profile image61
    hedgeekposted 15 years ago

    ** Spoiler II **
    Here's my solution:  Annie takes the flashlight, hits Bob, Cristy, and Dorothy in the head, pushes them each over the side of the bridge and then strolls across in about 5 minutes.  It turns out Annie is a sociopath.  This is an important fact that was somehow left out of the orignal description.  She also keeps a goalie mask in her backpack.

  9. Apae profile image60
    Apaeposted 15 years ago


    Why 17 minutes?

    Do they have an appointment on the other side of the bridge or something?

    That is the true question.

    Answer me that and I'll give you a cookie.

  10. sminut13 profile image61
    sminut13posted 15 years ago

    i think bothe livelonger and robin have given good suggestions but i'm gonna take robin's idea.
    annie crosses the bridge and helps to light up thus making the way brighter. (1 min)
    since bob is a guy,he can carry dorothy(assuming he can, grins) and cross but i'm gonna add some more time since dorothy seems to be more "afraid" you can say. so i would say he'd most likely take around 5-6 mins.(6 mins max)
    after that, cristy will cross the bridge.(5 mins)
    thus they'll more or less take 12-13 mins at the most.

  11. gamergirl profile image88
    gamergirlposted 15 years ago

    My solution:

    Don't post homework on hubpages. tongue

    1. Mark Knowles profile image59
      Mark Knowlesposted 15 years agoin reply to this

      Best solution so far.

      Do you have another homework question for us?

  12. nory mae profile image55
    nory maeposted 15 years ago

    help me...

  13. thooghun profile image95
    thooghunposted 15 years ago

    Riddle me this,

    "You are a contestant on the game show Let's Make a Deal, and emcee Monty Hall has a game for you to play.

    On stage are three huge doors, and he informs you that hidden behind one of the three doors is a brand new sports car, behind another is a donkey, and behind another is 400 pounds of bananas. (This may seem obvious, but your goal is to get the car, not the donkey or the bananas.)

    He asks you to choose one door, and you will win the prize behind that door. You choose, but before he reveals what you have won, Monty reveals what's behind one of the doors you did not pick, and it's not the car. Before revealing what lies behind the remaining two doors, he makes you one final offer: if you wish, you may switch from your choice to the other remaining door.

    The question is: Should you switch, should you not switch, or does it matter?"

  14. Misha profile image64
    Mishaposted 15 years ago

    LOL that's from university course on the probabilistic theory. I don't remember neither the answer, nor the mathematics involved big_smile

  15. thooghun profile image95
    thooghunposted 15 years ago

    It has been annoying me immensely. I believe it was originally connived by Vos Savant. I know the answer, but I still don't agree with it! I must have the IQ of a small rock.

  16. Mark Knowles profile image59
    Mark Knowlesposted 15 years ago

    My brain hurts just thinking about it and I know I'm not sleeping tonight until I have it worked out.

    Thanks a lot big_smile

  17. sminut13 profile image61
    sminut13posted 15 years ago

    lol, i need to read the ques again. probability question huh. hehehehe i used to kinda dislike tht topic during my high sch. hehehe well if one of the door he opened doesn't have car, then doesn't it mean tht there's a 50-50 chance of it being in yours?? if tht's the case, does switching or not really matter?? hmm unless it's like for example, the door tht didn't have was the first one. then maybe the car is in the sec one? i don know sometimes ppl like to put in alternate ways.
    but in my opinion it all boils down to luck too so i would probably go with my choice and not switch.

  18. Mark Knowles profile image59
    Mark Knowlesposted 15 years ago

    Dammit, this is still bugging me, but I am going with "It doesn't matter."

  19. thooghun profile image95
    thooghunposted 15 years ago


    Just a little background note. Vos Savant is the person with the highest IQ living today.

  20. Mark Knowles profile image59
    Mark Knowlesposted 15 years ago

    I am still not getting it. Guess I too have the I.Q. of a small rock. I like the analogy by the way big_smile

  21. caspar profile image60
    casparposted 15 years ago

    Hmm...I think my IQ must be that of a tiny piece of gravel...or maybe a grain of sand?

  22. kpfingaz profile image68
    kpfingazposted 15 years ago

    Vos Savant needs to get laid.

  23. rtfverterra profile image58
    rtfverterraposted 15 years ago

    I started to think I don't have an IQ. Waaaaa, mama help me out of this one.... yikes

  24. sminut13 profile image61
    sminut13posted 15 years ago

    i'm beginning to think my iq is disappearing too after lack of education. grins

  25. bloggerdollar profile image66
    bloggerdollarposted 15 years ago

    Monty Hall problem bugged me out years ago but I understood the idea at last and a relief got over my whole soul since then smile

    If you attend such a contest switch the door..

  26. Brian Murray profile image58
    Brian Murrayposted 14 years ago

    It's been a while since the question was posted, but I just happened upon it - so, here's my explanation as to why it IS better to switch.

    The key is to remember that there are two cases.  Either (1) you are going to stick with your door, or (2) you are going to switch. 

    Case 1:

    You are going to stick with your door.  Your original probability of choosing the correct door is 1 out of 3.  Just because one of the goats is revealed, doesn't change that probability.  So, if you are going to stick with your first choice, your probability of winning remains 1/3.

    Case 2:

    You are going to switch.  Well, you have a 2 out of 3 chance of picking the wrong door from the start.  If you did pick the wrong door, and then switch - you will be a winner.  So, you have a 2/3 chance of picking wrong to begin with, and then switching to the winner.

    Therefore, switching actually doubles your chances of winning.

    I hope that helps!

  27. dingdong profile image59
    dingdongposted 14 years ago

    Good one big_smile


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