What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

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 is more useful when it is broken?

A large container is kept in open under the rain. Every passing hour, the water collected inside the container becomes double what it was.

In ten hours, the container is filled completely. Can you calculate how long would it have taken to be filled in half?

In the given picture, you can find two letters missing. When two particular letters are placed in the missing spots, you get an eight-letter word while reading in the anti-clockwise direction. Can you find out the missing letters and the missing word eventually?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Which is the smallest number that you can write using all the vowels exactly once?

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

Identify the hidden meaning behind this picture?

The centre of the third figure is empty. What digit should fit inside?