It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

People make me, save me, change me, raise me. What am I?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

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?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

What work can one never finish?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

Why are all black people so quick ?