It is deaf, Dumb and Blind!!!

Still, always tells the truth. What is it?

Our product and our sum always give the same answer. Who are we?

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

Why is the Hole below a Lock?

What is the difference between a jeweller and a jailer?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

Can you make the below equation true by using any three numbers from "1, 3, 5, 7, 9, 11, 13 and 15"?

( ) + ( ) + ( ) = 30

At my favorite fruit stand,
an orange costs 18,
a pineapple costs 27,
and a grape costs 15.
Using the same logic, can you tell how much a mango costs?

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

If all Goats are Sheep and all Sheep are Deers, are all Deers Goats ?