Riddle Collection

A couple invited four other couple over to dinner. As people walk in, some of them shake hands with the others. No one shakes hands with his or her own date. After a while, the inviting husband looks at the nine other people and notices that each one shook a different number of hands. How many hands did his wife shake?

A ladder has ten steps. You start to climb the ladder, and in each move you can either climb one step up or directly two steps us. How many different ways are there to climb the lader?

How is it possible to cut a pizza into eight slices of the same size using only three cuts?

You stand in front of a 100 floors building, and are given two crystal balls. You can drop a ball from any floor to the ground, to see if it breaks. What is the minimum number of drops required to find out from which floor crystal balls break?

Use the number 1, 5, 6 and 7, one time each, and the four basic operations, to reach the number 21.

In an indian tribe, there are women cheating on their housbands (at least one). every housband in the group knows about all the ather women whether they cheat or not, besides his own. The chief of the tribe decided that all couples should stay in their tents without talking to any ather member of the tribe, untill the cheaters will be cought. He tells every man to shoot his wifes the morning after they found out she cheats.
in the sixth morning shots were heard in the camp. How many cheaters were there in this tribe?

(Know Math) You are a lion, hiding near a pack of 100 deer in the savanna. Deers cross your hiding spot one by one; when it does, you can see its weight. This is also your only chance of jumping out and hunting it. You remember the weight of the deers that already passed you, but of course you don't know anything about those who haven't passed yet. What will you do to ensure that you will eventually jump on the fattest deer in the pack with at least 25% chance of success?

An hungarian cube is composed of 27 connected cubes. The middle one has no facets which show on the outside (contain a colored square). How many cubes are there with one, two and three outer facets?

A math teacher invites all the teachers to his house and tells them: "I have three sons. The sum of their ages is the number of this house, and the product of their ages is 36. How old are they?" After a while the English teacher stands up and says: "There is one data mising". The math teacher responds: "True, my older son plays the piano". The English teacher replies that now he knows the answer.
How old were each of the math teachers' sons?

(Know Math) A soccer games ends with the result x:y (one team scored x goals and the other y goals). How many ways are there to reach this final score, if the game started at 0:0?

An infantry squad contains two infantry soldiers and one tank soldier, and a tank squad contains two tank soldiers and one infantry soldier. An infantry platoon contains two infantry squads and one tank squad, and a tank platoon contains two tank squads and one infantry squad. An infantry company contains two infantry platoons and one tank platoon, and a tank company contains two tank platoons and one infantry platoon. An infantry brigade contains two infantry companies and one tank company, and a tank brigade contains two tank companies and one infantry company. An infantry regiment contains two infantry brigades and one tank bridage, and a tank regiment contains two tank brigades and one infantry brigade.
You are the commander of an infantry regiment, and you receive an order to change into a tank regiment. How many infantry soldiers will have to be retrained to become tank soldiers?

Four prisoners are about to be executed. Two are wearing white hats, and two are wearing black ones. No one knows which hat he is wearing. One of the prisoners is standing alone in a separated room. The other three are standing in line in another room: The first of them is facing the wall, the second is facing the back of the first one (so he can see his hat), and the third one is facing the back of the second (so he can see both the first's and the second's hat).
The guards tell all four prisoners that if they can guess their hat's color, they'll be free, but if they guess wrong they will go through horrible tortures before death. One of the prisoners will walk free for sure - who is it and why?