Three people check into a hotel. They pay $30 to the manager and go to their room. The manager finds out that
the room rate is $25 and gives $5 to the bellboy to return. On the way to the room the bellboy reasons that $5
would be difficult to share among three people so he pockets $2 and gives $1 to each person. Now each
person paid $10 and got back $1. So they paid $9 each, totalling $27. The bellboy has $2, totalling $29. Where
is the remaining dollar? 
Solution

Ages

Ten years from now Tim will be twice as old as Jane was when Mary was nine times as old as Tim.
Eight years ago, Mary was half as old as Jane will be when Jane is one year older than Tim will be at the
time when Mary will be five times as old as Tim will be two years from now.
When Tim was one year old, Mary was three years older than Tim will be when Jane is three times as old
as Mary was six years before the time when Jane was half as old as Tim will be when Mary will be ten
years older than Mary was when Jane was one-third as old as Tim will be when Mary will be three times
as old as she was when Jane was born. How old are they now? 
Solution

Camel

An Arab sheikh tells his two sons to race their camels to a distant city to see who will inherit his fortune. The one
whose camel is slower will win. The brothers, after wandering aimlessly for days, ask a wise man for advise.
After hearing the advice they jump on the camels and race as fast as they can to the city. What does the wise
man say? 
Solution

Elimination

97 baseball teams participate in an annual state tournament. The way the champion is chosen for this
tournament is by the same old elimination schedule. That is, the 97 teams are to be divided into pairs, and the
two teams of each pair play against each other. After a team is eliminated from each pair, the winners would be
again divided into pairs, etc. How many games must be played to determine a champion? 
Solution

Locks and Boxes

You want to send a valuable object to a friend. You have a box which is more than large enough to contain the
object. You have several locks with keys. The box has a locking ring which is more than large enough to have a
lock attached. But your friend does not have the key to any lock that you have. How do you do it? Note that you
cannot send a key in an unlocked box, since it might be copied. 
Solution

Mixing

Start with a half cup of tea and a half cup of coffee. Take one tablespoon of the tea and mix it in with the coffee.
Take one tablespoon of this mixture and mix it back in with the tea. Which of the two cups contains more of its
original contents? 
Solution

Ropes

Two fifty foot ropes are suspended from a forty foot ceiling, about twenty feet apart. Armed with only a knife,
how much of the rope can you steal? 
Solution

Hats

Three logicians, A, B, and C, are wearing hats, which they know are either black or white but not all white. A can
see the hats of B and C; B can see the hats of A and C; C is blind. Each is asked in turn if they know the color
of their own hat. The answers are: A: "No." B: "No." C: "Yes." What color is C's hat and how does she know?
Solution
 

Weighing / Balance

You are given 12 identical-looking coins, one of which is counterfeit and weighs slightly more or less (you don't
know which) than the others. You are given a balance scale which lets you put the same number of coins on
each side and observe which side (if either) is heavier. How can you identify the counterfeit and tell whether it is
heavy or light, in 3 weighings?

More generally, you are given N coins, one of which is heavy or light. 
Solution