What you cannot hold but it is yours?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

If two fifty-foot ropes are suspended from a forty-foot ceiling that is twenty feet apart, how much rope will you be able to steal if you have a knife?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different.

How do you measure 45 minutes?

You see me once in June, twice in November, and not at all in May. What am I?

Move four matchsticks to the below square to form three squares?

When 99 is considered higher than 100?

In a stable, there are men and horses. In all, there are 22 heads and 72 feet. How many men and how many horses are in the stable