What always comes into a house through the keyhole?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

If 21x = 79x, what is the value of x?

What has one eye, but can’t see?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

What number do you get when you multiply all of the numbers on a telephone's number pad?

Why Aeroplane windows are round?

Identify The phrase in the picture.

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?