How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

A sundial has the fewest moving parts of any timepiece. Which has the most?

A boy and his father are caught in a traffic accident, and the father dies. Immediately the boy is rushed to a hospital, suffering from injuries. But the attending surgeon at the hospital, upon seeing the boy, says 'I cannot operate. This boy is my son.' How is this situation explained?

I’m tall when I’m young, and I’m short when I’m old. What am I?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

On rolling two dices (six-sided normal dice) together, what is the probability that the first one comes up with a 2 and the second one comes up with a 5?

What is the next number?

77, 49, 36, 18 ?

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

You have a square. What you have to do is cut and reassemble the square such that you create a Red Cross sign that has the same volume as that of the square.