You're in a room with 3 light switches. Next to your room is another room with the door closed. Inside that room are 3 lights. You do not know which switch controls which light. How can you figure out which switch controls which light? You can only enter the room with the lights once.
Turn one switch on and leave it on for 1 hour. This is switch A. After the hour is up turn the light off and turn another light on (switch B). Go in to the room with the lights. The light that’s hot is light A. The light that is on is light B. and the light that is off, but not hot is light C.
A farmer has a sack of grain, a chicken and a fox. He has to get them across the river and he can't go around or fly but he does have a boat. He can only take one thing at a time across the river. How can he get them across?