What goes up but never comes down?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

I’m tall when I’m young, and I’m short when I’m old. What am I?

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

I know a nine-letter word having only one vowel.
Do you ?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

Which is the correct shadow of the bird?

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?