Some riddles:
Three Dots
The King is about to die. He sends messengers throughout the land seeking for the 3 smartest people. Finally 3 are found. He gives them a task to see which one is the wisest. He tells them, "I will seat you in a triangle so that each of you faces the other two. Then I will blindfold you and paint either a red or a green dot on each of your foreheads. When I remove the blindfolds each of you must raise your hand if you see any green dots. As soon as you have figured out what color your own dot is, lower your hand and tell me." So he seats them, blindfolds them, and then paints a green dot on all three foreheads. When the blindfolds are removed, all three hands go up. After a long pause, one hand comes down and the man says, "Your highness, I have a green dot." How did he know?
Lying Defeated
You are visiting an island on which two tribes of natives live. One tribe has black soles and always lies; the other tribe has white soles and always tells the truth. There are three natives standing near you. You can't see the bottoms of their feet, and indeed you find out it is extremely rude to look at another's soles, but you are curious so you ask the first man, "Sir, what color are your soles?" Now he happens to understand English, but he can't speak it, so he replies in his native tounge, "Glub Glub". You turn to the second man and ask, "Sir, what did he say?" The second man replies, "He said he had white soles" Now to be sure, you turn to the third and ask, "Sir, what color of soles does this second man have?" The third man replies, "Sir, he has black soles." Now the question is, what color of soles does the third native have?
Crossing A Bridge
"U2" has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each band member walks at a different speed. A pair must walk together at the rate of the slower man's pace :
Bono : 1 minute to cross
Edge : 2 minutes to cross
Adam : 5 minutes to cross
Larry : 10 minutes to cross
For example: if Bono and Larry across first, 10 minute have elapsed when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission.
Light Bulb Puzzle
There is a room with three light bulbs (in sockets). Outside the room there are three light switches which are connected to the bulbs inside the room, though you can't tell which switch is connected to which bulb. You can't see inside the room, and you're only allowed to go inside once. How do you find out which light switch is connected to which bulb?
Two Ropes
There are two uneven ropes that will take exactly an hour to burn each. These two ropes have different length. Now using these two ropes, you need to measure 45 minutes. You cannot assume that folding or burning half of a rope is 30 minutes since it is uneven, for example, it might take 30 minutes to burn 15% of one rope. How can you measure 45 minutes by using only these two ropes and a box of matches?
Ball-Bearing
A Supervisor in a Ball-Bearing factory receives a Memo from management saying that one of the 10 machines he manages is messing up, that machine is producing 9g bearings instead of 10g. The problem is that they don't know which machine is messing up. Management gave him a scale and they allowed him to use it only once to figure out the bad machine. How did he do it?
Hats
There are 3 black hats and 2 white hats in a box. Three men (we will call them A, B, & C) each reach into the box and place one of the hats on his own head. They cannot see what color hat they have chosen. The men are situated in a way that A can see the hats on B & C's heads, B can only see the hat on C's head and C cannot see any hats.
When A is asked if he knows the color of the hat he is wearing, he says no.
When B is asked if he knows the color of the hat he is wearing, he says no.
When C is asked if he knows the color of the hat he is wearing, he says yes and he is correct.
What color hat and how can this be?
Hourglasses
You have two hourglasses : a 4-minute glass and a 7-minute glass.
You want to measure 9 minutes.
How do you do it?