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?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

If six children and two dogs were under an umbrella, how come none of them got wet?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

I have nine bottles of wine and one of the nine bottles is poisoned.
I need to find the poisoned bottle with two facts
(1) Poison is deadly, only a sip will cost death
(2) I have two mice to do so.

How should I do it?

How many triangles are there on the puzzle below?