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Wednesday, 18 December 2013

Problem Solving - Riddle

My life is often a volume of grief, your help is needed to turn a new leaf. Stiff is my spine and my body is pale, but I'm always ready to tell a tale. What am I?

2.Brothers and sisters, I have none but this man's father is my father's son. 
Who am I looking at?

You are shown two doors - one leading to hell and the second one to heaven and only the door guards know what is behind the doors. One guard is always lying and the other is always telling the truth (of course, you don't know who is lying). You can ask only one guard one question. 
What question can get you to heaven?

If you had a 5-liter bowl and a 3-liter bowl, and an unlimited access to water, how would you measure exactly 4 liters?

If someone says "I always lie", are they telling the truth? Or are they lying?

1 comment:

  1. 3. The solution to the original problem is ”If I were to ask the other guard which door goes to
    heaven, what would he say?” If you ask the liar, he will lie about what the truth-teller would say,
    and point you to the door that goes to hell. The truth teller would tell the truth about how the liar
    would give the wrong door, and would also point you toward the door to hell. Thus, you take the
    other door.
    For the version with only one guard, we ask ”If I were to ask
    which door goes ot heaven,
    what would you say?”. The truth teller would tell the truth and point you to the door to heaven.
    The liar would lie about what he
    say if you asked him. If you did ask him, he would tell
    you the door to hell, so he lies about this also also points you toward the door to heaven. Thus both
    would point you toward the correct door. So, you don’t need two guards, you only need one guard
    that either always lies or always tells the truth! This is also the solution to the problem with two
    guards, where you don’t know how many tell the truth and how many lie - you just ignore one of