Fake Coin!

There are 100 gold coins in 10 columns by 10 coins in each column. Every coin weights 1 lb. One column contains 10 fake coins.Each coin in it weights 0.9 lb. Take one measurement to find the column with fakes.

Switch Room!

There are 3 switches in one room that control 3 electrical lamps located in the other room.You are allowed to spend 5 minutes in the room with switches,change their position as you want.Then you should go to the room with lamps and tell exactly what switch controls every lamp.You can't return to the room with switches.

Connect nine dots with four lines

o    o    o

o    o    o

o    o    o

Do not cross the same dot twice.

Two Candles!

You have 2 candles. Every candle lights for 60 minutes. You have to find the way to measure 45 minutes.

Water In pot!

There is a pot full of water. How to pour out half of it without using a meter?