Logic Puzzles

6. The Double Jeopardy Doors

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.

There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.

You can, however, ask one robot one question. The problem is one robot always tells the truth ,the other always lies and you don't know which is which.

What is the question you ask?

Added 1 January 2007

Hint:

The two robots know each others personality. That they talk when they're bored, lonely, etc. Try to get the two robots to cancel their evil & good ways out.

Solution: Ask one robot what the other robot would say, if it was asked which door was safe. Then go through the other door.

Comments (13)

Anonymous 16 December 2008

Puzzle #6 is correct, but I find it quite silly.

Anonymous 18 May 2010

For problem number 6, could the solution Cube One: 1, 2, 4, 0, 5, 6 and Cube Two: 3, 1, 2, 7, 8, 0 also be acceptable? Please clarify if there are any mistakes in this alternate answer.

Anonymous 28 February 2011

Another answer to question no 6 could be 5^5,000,000,000 as the question defines that all left hands have five fingers per hand.

Anonymous 12 May 2011

The solution to puzzle number six seems to require adding the number of fingers on each person's hand before multiplying, which feels like a stretch to fit into the series.

Anonymous 28 February 2012

Currently, the Earth's population is about seven billion, not five billion.

Anonymous 12 August 2012

Number six could also be a step-father, since it doesn't say the gender and the child is still legally his son.

Anonymous 19 February 2013

Question 6 is logically incorrect unless you count the fingerless person as the last multiplication function.

Anonymous 5 October 2013

You might as well include the 9; since there isn't a day of the month in 00.

Anonymous 27 October 2014

The question "Is the door which leads to freedom also the door which is guarded by the robot who only tells the truth?" provides the same answer as the question "Are you guarding the door that leads to freedom?"

Anonymous 19 March 2015

Ask any of the robots if he is a robot. If the robot says no, it is lying; otherwise, it is not. Then choose any one door and ask the other about the door. If it lies, choose the door; else walk through the same door.

Anonymous 19 March 2015

An alternative solution to The Double Jeopardy Doors is to ask any robot if it is a robot. If it says no, it is lying; if it says yes, it is telling the truth. Then, choose one door and ask the other robot about it.

Anonymous 25 December 2016

The answer to the puzzle is likely '2' because the number on the dice does not affect the outcome.

Anonymous 31 August 2017

The wording of question six is unclear and needs improvement to enhance user experience.

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