Numbers in mind puzzle

441.6K Views

John has one of the numbers 1, 2, or 3 in mind. Jacob is allowed to ask one question to John to find out which of these three numbers he has in mind. John will answer this question only with the answers “yes”, “no”, or “I don’t know”.

Which question should Jacob ask John to find out in one time which number he has in mind?

Share
SherlockHolmes Expert Asked on 25th January 2018 in Logic Puzzles.
Add Comment

  • 3 Answer(s)

    I found a simpler answer than the one i gave above. Jacob will ask:
    If you subtract 2 from your number,  will the result be positive?
    No means the chosen number is 1.
    I don’t know the chosen number is  2 (since zero in neither positive nor negative)
    Yes means the chosen number is 3.

    Moshe Scholar Answered on 31st January 2020.
    Add Comment

    Jacob will ask “Is the number in your mind greater than 2″?
    If John says”Yes”, then it is obviously 3.
    If he says”No”, then it is obviously 1.
    If he says”I don’t know”, then it is 2 because, 2 is not greater than 2.
    Similarly the question can be asked as ” Is the number in your mind less than 2″? and the same strategy be applied.

    Rahim Starter Answered on 10th March 2018.

    Answer for question “Is the number in your mind greater than 2″  NO means it can be 1 or 2 any of the number.

    on 2nd August 2018.
    Add Comment

    Jacob will  ask: If I’ll draw a function of the degree of the number you have chosen will it have extremum?
    A 1st degree function is a straight line so the answer is no.
    A 2nd degree function has an extremum point so the answer is yes.
    A 3rd degree function might  have an extremum point but not always’ so the answer will be “I don’t know”

    Moshe Scholar Answered on 31st January 2020.
    Add Comment
  • Your Answer

    By posting your answer, you agree to the privacy policy and terms of service.
  • More puzzles to try-