I am white when I am dirty, and black when I am clean. What am I?

Can you find out a way through which you can make five squares out of the given figure by moving just six match sticks?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

The answer I give is yes, but what I mean is no. What was the question?

What does man love more than life, and hate more than death or mortal strife; that which satisfied men want; the poor have, and the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

What is the relationship between these matchstick pictures below?

What jumps when it walks and sits when it stands?

Can you solve the maths in the below-given picture equation?

John was writing his first book. After saving the document, he locked his laptop with a password and mentioned some phrases for the hint box.

A friend of his tried opening his laptop but found out that it was password protected. Following is the hint that appeared.
1 mobile 3 books 2 roars 1 night 4 balls 2 lighters 1 ghost 1 hat 3 watches.

Can you help him in cracking the password?