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

What do you think with the below Picture ?

Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

I don't get anymore wetter, no matter how much rain falls on me.

What goes up but never comes down?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

A professor thinks of two consecutive numbers between 1 and 10.
'A' knows the 1st number and 'B' knows the second number

A: I do not know your number.
B: Nor do I know your number.
A: Now I know.

What are the four solutions for this?