What has many keys but can’t open a single lock?

If an earthquake is 1 point higher on the Richter Scale than another earthquake which is actually 10 times stronger, how much stronger would an earthquake be if it was just half a point higher on the Richter scale?

What Adam and Eve do not have but the rest of the people have?

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Three ants are going up a hill, one behind the other. The last ant then says to the other ants, 'There is an ant behind me!'' How come?

What you cannot hold but it is yours?

How can you make number one disappear by adding something to it?

I look flat, but I am deep. Hidden realms I shelter. Lives I take, but the food I offer. At times I am beautiful. I can be calm, angry, and turbulent. I have no heart but offer pleasure as well as death. No man can own me, yet I encompass what all men must have. What am I?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?