There is a house. One enters it blind and leaves it seeing. What is it?

Three men go to stay at a hotel and they are charged \$30 for the room.

They split the cost with ten dollars each.

Later the manager finds out that the rate is \$25 and gives the bellboy \$5 to return to the guests. On the way to the room the bellboy reasons that \$5 would be difficult to split among three people so he pockets \$2 and gives \$1 to each person.

Now each person paid \$10 and got back \$1. So they paid \$9 each, totalling \$27. The bellboy has another \$2, adding up to \$29. Where is the missing dollar?

How many squares are in this picture?

King Octopus has servants with six, seven, or eight legs. The servants with seven legs always lie, but the servants with either six or eight legs always say the truth.

One day, 4 servants met:
The blue one says: “Altogether we have 28 legs”;
The green one says: “Altogether we have 27 legs”;
The yellow one says: “Altogether we have 26 legs”;
The red one says: “Altogether we have 25 legs”.

What is the colour of the servant that is speaking the truth?

Four glasses are placed on the corners of a square Lazy Susan (turntable). Some of the glasses are upright (up) and some upside-down (down).

A blindfolded person is seated next to the Lazy Susan and is required to re-arrange the glasses so that they are all up or all down, either arrangement being acceptable.

The glasses may be re-arranged in turns subject to the following rules.

1. Any two glasses may be inspected in one turn and after feeling their orientation the person may reverse the orientation of either, neither or both glasses.
2. After each turn the Lazy Susan is rotated through a random angle.
3. At any point of time if all four glasses are of the same orientation, a bell will ring.

Can you devise an algorithm which allows the blindfolded person to ensure that all glasses have the same orientation (either up or down) in a finite number of turns? The algorithm must not depend on luck.