Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

Why did Navjot Singh Sidhu put the new January calendar in the freezer

Once while in his court, King Akbar asked Birbal to write something on a wall that makes one sad when read in good times and makes one happy when read in sad times.

He took only a few moment and wrote something that fit the requirements. What did he write?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

For an extra income, John decided to work at a Hotel for one hour daily. The manager offers him that they will pay him $11 after every 11 days.
However, John offered a different proposition to the manager. The offers stand as:
He will be paid just a penny on his first day.
Two pence will be paid on the second day,
Four pence will be paid on the third day.
And so on till the 11th day.

Should the Hotel manager accept his offer?

How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

What runs around the whole yard without moving?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

I know a number which is spelt in alphabetical order.
Do you?