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?

Take one out and scratch my head, I am now black but once was red. What am I?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

10 people came into a hotel with 9 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the tenth guest to wait for a little with the first guest in room number 1. So in the first room, there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, ..., and the ninth guest to room number 8. Then he returned to room number 1 and took the tenth guest to room number 9, still vacant.
How can everybody have his own room?

What came first, the chicken or the egg?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

If 24H in a D => 24 hours in a day.
What does "64S on CB" stand for?

In the below-given picture of a pretty girl, there is something wrong. Can you find out what it is?

Count the squares in the matchstick puzzle below?