I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

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

As shown in the image, the nine Dogs are square fenced. By constructing just two square fences can you make sure that two Dogs cannot meet each other without crossing the fence?

How many times can you subtract the number two from the number fifty?

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?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

1. What does:
TIM JOB
represent?

2. What does:
MO_ _
represent?

Why do people go to bed?

Which alphabet letter is a question?