Logic Puzzles

ecco un pò di quelli che si chiamano "Logic Puzzles"...coraggio, divertitevi!!

sono in inglese, per "stuzzicare" ulteriormente la vostra mente!

1)

A Ping-Pong Ball in a Hole

Your last good ping-pong ball fell down into a narrow metal pipe imbedded in concrete one foot deep.
How can you get it out undamaged, if all the tools you have are your tennis paddle, your shoe-laces, and your plastic water bottle, which does not fit into the pipe?

2)

The Ball

How can you throw a ball as hard as you can and have it come back to you, even if it doesn't bounce off anything? There is nothing attached to it, and no one else catches or throws it back to you.

3)

Virile Microbes

A Petri dish hosts a healthy colony of bacteria. Once a minute every bacterium divides into two. The colony was founded by a single cell at noon. At exactly 12:43 (43 minutes later) the Petri dish was half full.
At what time will the dish be full?

4)

The Castle

A square medieval castle on a square island is under siege. All around the castle there is a square moat 10 meters wide. Due to a regrettable miscalculation the raiders have brought footbridges, which are only 9.5 meters long. The invaders cannot abandon their campaign and return empty-handed.
How can the assailants resolve their predicament?

SOLUZIONI:

1) All you have to do is pour some water into the pipe so that the ball swims up on the surface.

2) Throw the ball straight up in the air.

3) The dish will be full at 12:44.

4) You can put one foot-bridge over one corner (thus a triangle is created). Then from the middle of this foot-bridge lay another foot-bridge to the edge (corner) of the castle. You can make a few easy equations confirming that this is enough.