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

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?

O_er_t_o_

Complete the missing letters of the given word.

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

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

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?