Princess, Flowers and Snake With Incorrect Name Plates

There are three rooms, and there are Princess, Flowers and Snake in those rooms. The doors of all the rooms have incorrect nameplates. i.e., the nameplate for the princess' room is not Princess. Similarly, the nameplate for the Flowers' room is not Flowers. You need to find the room of the Princess without going to the room of Snake. How do you find?



Answer:

Go to the room which has the nameplate Snake. That will not have Snake. If the room has princess, you are done. If the room has flowers, then go to the room which has nameplate flowers. Princess would be there in that room. [Since, Princess cannot be there in the room which has nameplate Princess.]

One Person Always Lies, Another always Tells Truth

You have to go to a place and there are two paths. You don't know which path leads to your destination. There are two watchmen at the entrance. One person always tells truth, and another one always tells lies. You can ask only one question to one person. What question would you ask to find the way to your destination?



Answer:
If I ask the other person, the way to the destination, what would he tell?

Whatever he says, that is not the correct path. Take the other path.

Four People crossing the river with different speeds

There is a dark tunnel and four people wants to cross the tunnel. In the tunnel, only two people can travel at a time, and there is only one torch light. Without the torch light, they cannot travel through the tunnel. The four people can travel with different speeds. The first person takes 1 hour to travel through the tunnel. Second person takes 2 hours, third person takes 5 hours, and fourth person takes 10 hours. How can they travel in the least amount of time?



Solution:

1 & 2 cross the tunnel

1 returns

5 & 10 cross the tunnel

2 returns

1 & 2 cross the tunnel

Total Time: 17 hours