Question

Suppose there are signs on the doors to two rooms. The sign on the first door reads “In this room there is a lady, and in the other one there is a tiger”; and the sign on the second door reads “In one of these rooms, there is a lady, and in one of them there is a tiger.” Suppose that you know that one of these signs is true and the other is false. Behind which door is the lady?

Short answer

The second door sign is true.

Step-by-step solution

Tips

Puzzles that can be solved using logical reasoning are known as logic puzzles.

Solving logic puzzles is an excellent way to practice working with the rules of logic.

Solving logic puzzles

If the first sign were true then the second sign would also be true.

In that case, we could not have a true sign and a false sign.

Therefore, the second sign is true and the first is false.