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.
Think about sending the box to your friend in multiple stages, with each stage adding an extra layer of security...
Attach a lock to the ring. Send it to her. She attaches her own lock and sends it back. You remove your lock and send it back to her. She removes her lock.
I am something people love or hate. I change people's appearances and thoughts. If a person takes care of them self I will go up even higher. To some people, I will fool them. To others, I am a mystery. Some people might want to try and hide me but I will show. No matter how hard people try I will Never go down. What am I?
Only one color, but not one size, Stuck at the bottom, yet easily flies. Present in sun, but not in rain, Doing no harm, and feeling no pain. What is it?
Who is that with a neck and no head, two arms and no hands? What is it?
If eleven plus two equals one, what does nine plus five equal?
How can you write down eight eights so that they add up to one thousand?
It can't be seen, can't be felt, can't be heard, and can't be smelt. It lies behind stars and under hills, And empty holes it fills. It comes first and follows after, Ends life, and kills laughter. What is it?
What English word retains the same pronunciation, even after you take away four of its five letters?
Three playing cards in a row. Can you name them with these clues? There is a two to the right of a king. A diamond will be found to the left of a spade. An ace is to the left of a heart. A heart is to the left of a spade. Now, identify all three cards.
What is it that given one, you'll have either two or none?
George, Helen, and Steve are drinking coffee. Bert, Karen, and Dave are drinking soda. Using logic, is Elizabeth drinking coffee or soda?
When John was six years old he hammered a nail into his favorite tree to mark his height. Ten years later at age sixteen, John returned to see how much higher the nail was. If the tree grew by five centimeters each year, how much higher would the nail be?
I am four times as old as my daughter. In 20 years time I shall be twice as old as her. How old are we now?
Which of the following words don't belong in the group and why? CORSET, COSTER, SECTOR, ESCORT, COURTS
Lily is a lilypad in a small pond. Lilly doubles her size each day, On the 20th day she covers the whole pond. On what day was Lily half the size of the pond?
What common English verb becomes its own past tense by rearranging its letters?
The ages of a father and son add up to 66. The father's age is the son's age reversed. How old could they be? (3 possible solutions).
There was a man who was born before his father, killed his mother, and married his sister. Yet, there was nothing wrong with what he had done. Why?
There are two sisters; one gives birth to the other, who in turn gives birth to the first. Who are they?
What two whole, positive numbers have a one-digit answer when multiplied and a two-digit answer when added?
Which word is the odd one out: Seventy, Brawl, Clover, Proper, Carrot, Swing, Change, Travel, Sacred, Stone?