Logic puzzle 1 (Easy)

Logic Level 2

You saw 3 doors in front of you, one door leads to the exit, the others lead to a bottomless pit. Each door has a note in front of it.

The first door said: It is untrue that the second is not the exit

The second door said: The third door leads to a bottomless pit

The third door said: The exit is not behind this door

Given that the door with the exit has a false note, which door is the exit?

Not enough information Second door First door Third door

2 solutions

André Hucek
Dec 10, 2017

It is obvious that only one door contains a false note, further let $A$ be the first door, $B$ the second and $C$ the third. And $n_A$ note on $A$ , $n_B$ note on $B$ and $n_C$ note on $C$ .

$1)$ If $n_B$ would be false, (i.e $C$ is the exit door), then $n_C$ would automatically become also false. If $n_C$ is false (i.e $C$ leads to the exit), $n_C$ would create a paradox.

Therefore, $n_A$ is false and so $A$ is the exit.

$2)$ In this case it is more simple to do the opposite, (to apply whether $n$ is true), by which we immediately obtain $A$ again.

@Andrew Hucek , Líbí se mně tvůj nový profilový obrázek ;)

A Former Brilliant Member - 3 years, 5 months ago

Děkuju :-)

André Hucek - 3 years, 5 months ago

Anthony Xu
Dec 11, 2017

Assume the first door is the exit, then the note on it is false. The statement on the first door's note has a double negative, which means it is saying "the second door is the exit". In this case this statement is false. The second and third door are both correct because the third door is a bottomless pit.

If you assume the second or third door is the exit, there will be a contradiction.

Uh hello? You only mention that the exit have a false note but nothing about the others, so they can be both true and false. I think you should check back (I don't want anyone to report you).

Bách Hữu Trần - 10 months ago

Logic puzzle 1 (Easy)

2 solutions

0 pending reports