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

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

John was piloting a plane behind a car but was never able to overtake it. Why?

How many times can you subtract the number two from the number fifty?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

How far can you walk into the woods?

You are given 2 eggs.
You have access to a 100-storey building.
Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor, Both eggs are identical.
You need to figure out the highest floor of a 100-storey building an egg can be dropped without breaking.
Now the question is how many drops you need to make. You are allowed to break 2 eggs in the process

Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

When a clock is observed, the hour hand is at a minute mark and the minutes hand is six minutes ahead of it.

When the clock is observed again after some time, the hour hand is precisely on a different minute mark and the minute hand is seven minutes ahead of it.

Can you calculate how much time has elapsed between the two observations?