The more of this there is, the less you see. What is it?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

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

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

It can be easily calculated that the digits 0 to 9 can be arranged into 3628800 distinct ten-digit numbers.

But do you know how many of these numbers are prime?

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

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

If an electric train is travelling south, then which way is the smoke going?

A person was found dead on a big green land with no trees or buildings around. When the police arrived, they found a piece of rock lying next to him and the man was wearing clothes comprising of red, blue and yellow colours.

Can you tell who the person is and what was the cause of death?

How can you take 2 from 5 and leave 4?