I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

I get hot but I never sweat,
I cook food but I am not a chef,
I have a door but you can't enter me,
I have a light but I am not a lamp.
Who am I?

How many times can you subtract the number 5 from 25?

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?

Kids with the most attentive eyes can spot a different watermelon in 4 seconds. Can you? Test your eyes now!

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

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