What is black when you buy it, red when you use it, and gray when you throw it away?

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

After a heavy Thanksgiving meal, the night watchman went to work. In the morning, he told his boss he had dreamed that a saboteur planted a bomb in the factory and that he felt it was a warning. The boss promptly fired him. Worker confused, Why boss fire him?

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

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

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?

Find the missing number in the image below.

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

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