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

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

A sea diver is a real show-off. He showed everyone that he can hold his breath underwater for 15 minutes.

I went to the diver and told him that I can be underwater for double the time i.e 30 minutes.
He responded that he will give me 100$ if I would be able to do it. I won 100$.

What did I do?

Replace the question mark with the correct number in below Picture:

Can you place three balls such that the equation shown in the picture holds true?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

Which of the below owl is odd one out?

What number comes next in this sequence:
7 8 5 5 3 4 4 _

A horse was tied to a rope 5 meters long and the horses food was 15 meters away from the horse. How did the horse reach the food?