What is black when you buy it, red when you use it, and gray when you throw it away?

What brings you down but never up?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

Who can jump higher than a Mountain?

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?

Solve the mathematical equation in the picture below.