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

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

A 52% bias toss for head using the 51% tail bias coin was done to obtain a fair result.

Can you find how bias is the floor in this case?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

What does this rebus mean?

O
N
C
E
TIME

Imagine you are in a room with no windows or doors. How will you get out?

What has 88 keys?

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

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

Count the number of triangles in the picture below: