How can you tell a raw egg from a hard-boiled egg?

If eleven plus two equals one, what does nine plus five equal?

If you say my name, I will no longer exist. What am I?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Why do we preferably have round manhole covers and not square ones?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

A prisoner is told: "If you tell a lie, we will hang you and if you tell the truth, we will shoot you." What did the prisoner say to save himself?

Find the next number in the sequence

5 12 24 36 ?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Given that

(78)^9 = 6
And (69)^4 = 11

Can you find out

(99)^2 =?

(Note: This is Logical, not Mathematical)