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?

I have teeth but i don't bite. Who Am I ?

What goes up but never comes down?

What has one eye, but can’t see?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

There are two dice with empty faces in front of you and a marker. You can mark any number on each of the faces of the two dice, but you have to display all 31 days of the month using the two of them.

Which numbers will you mark on which dice so that you can easily depict all the dates of the month?

A patient was diagnosed with some ailment. He was given five different tablets to take at night at an interval of 15 minutes.

How long will it take the patient to consume all the five tablets?

It spends most of its day eating white, but when it’s quick enough, it gets to eat fruit and sometimes some blue things. It’s in a dark room, where the walls are blue, it runs from a ghost that roams the halls and haunts it all the time. What is it?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

I am a prime number.
The double of myself is equal to the square of me.

which number am I?