When my father was 31 I was 8. Now he is twice as old as me. How old am I?

What always comes into a house through the keyhole?

How can you drop a raw egg from a height onto a concrete floor without cracking it?

A man dies of old age on his 25 birthday. How is this possible?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

What is the Surname of Barbie Doll?

When is the top of a mountain similar to a savings account?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?