1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is this a trick question?

  1. Dec 10, 2011 #1
    Question
    When I went to class yesterday there was a problem on the board and it said..
    "If you were to pick an answer to this problem what is the probability you would get it correct?
    1. 25%
    2.50%
    3.0%
    4.25%

    My answer
    This question seems flawed because how could someone possibly choose an answer if they don't know how many possible incorrect "things" they could choose. And it is impossible to have a 25% chance, a 0% chance and a 50 % chance at the same time because if you knew the ratio of what the "correct" answer is out of all the possible answers you would know that you either have a 0% 44%..100% or what ever it might be. But with out knowing this fact it seems impossible to know.

    This is what I have decided... because the problem is giving me 4 possible answers I am going to read into this and assume the problem is actually saying that I have 4 bags labeled 1. 2. 3. and 4. which have a probabiliy of picking the correct answer of 25%, 50%, 0% AND 25% respectfully. I will also assume in each bag there are four marbles, one marble is red and in order to be "correct one must pick the red marble.
    first bad there is one red marble
    second bad there are two red marbles
    third bag there are no red marbles
    fourth bad there is 1 red marble
    Next inorder for this to be accurate I would have to put all the marbles from bags 1,2,3,4 into one bag...thus there is a total of 16 marbles in which there is 4 red marbles which gives me a 25 percent change of chosing the red marble... the correct answer.
    Is this correct?
     
    Last edited: Dec 10, 2011
  2. jcsd
  3. Dec 10, 2011 #2
    nvrmind...perhaps this. This answer can't be 0, because we know there is a chance you would get it right, but that leaves, 3, two of which are the same, so that leaves 2, so you have a 50% chance to get it right?
     
  4. Dec 10, 2011 #3
    Que?
     
  5. Dec 10, 2011 #4
    Sorry...I had typed something really stupid, even for me...so I changed it
     
  6. Dec 10, 2011 #5
    Seems like a trick question because on the other hand, if you couldn't use the fact that it won't be 0, then with 2 answers the same it is 33%, which isn't there so you have a 0% of getting it right...ha Quite a brain teaser indeed We need someone smarter to answer this one.
     
  7. Dec 10, 2011 #6
    Lol I first thought it was 33 percent... but then as i explained above now im thinking it's 25 but im not sure.
     
  8. Dec 11, 2011 #7
    If there are four answers, then only if you have no idea which is the correct one and all of them seem equally likely, and you choose one answer at random, the chance of it being right is 25%. But that isn't the case here. We've already eliminated 0% as a possible correct answer which means that none of the other answers can be correct either. Yet if we choose 0%, that is obviously incorrect.

    My guess is that there is no answer to this problem.
     
  9. Dec 11, 2011 #8
    if the answer is 25% then the probability you are correct becomes 50%
    if the answer is 50% then the probability you are correct becomes 25%
    if the answer is 0% then the probability you are correct becomes 25%

    at least that's how I've come to understand it, there is no answer to the problem
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Is this a trick question?
  1. Subset Question (Replies: 3)

  2. Probability Question (Replies: 12)

Loading...