What always comes into a house through the keyhole?

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

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

Arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 above and below the division line in a manner that the thus formed fractions equal to 1/3.

(You can use one number only once)

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

Identify The phrase in the picture.

What breaks yet never falls, and what falls yet never breaks?

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