What number should come in place of the question mark below?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

The pound is not a finish.

We are sharing a few instructions below, which you have to use in any suitable order to modify the above sentence such that the end sentence is a scientific fact.

- Eliminate a letter and supplement another in its place.
- Take away one word.
- Remove one letter from one word.
- Get rid of two letters from one word.
- Swap a word with its antonym.

If your uncle’s sister is not your aunt, what relation is she to you?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

You need to move three matchsticks to form three squares. Can you do it?

Move three sticks of the spiral below to form a square.

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

10 people came into a hotel with 9 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the tenth guest to wait for a little with the first guest in room number 1. So in the first room, there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, ..., and the ninth guest to room number 8. Then he returned to room number 1 and took the tenth guest to room number 9, still vacant.
How can everybody have his own room?

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?