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 has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

What word is represented by this rebus?

My first is in chocolate but not in ham. My second is in cake and also in jam. My third at tea time is easily found. Altogether, this is a friend who is often around. What is it?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

You need to move three matchsticks to form three squares. Can you do it?

Can you name some countries which do not have the alphabet 'A' in them?

How do you go from 98 to 720 using just one letter?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?