Eight of us go fourth, not back, to protect our king from an attack. What are we?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Here is what you have to do. You have to throw a ball as hard as you can but it must return back to you even if it does not bounce at anything. Also, you have nothing attached to the ball. There is no one on the other end to catch that ball and throw it back at you.

How will you do it?

You need to move three matchsticks to form three squares. Can you do it?

Two natural numbers have a sum of less than 100 and are greater than one.

John knows the product of the numbers and Jacob knows the sum of numbers.

The following conversation takes place between them:
John: 'I am not aware of those numbers.'
Jacob: 'I knew you wouldn't be. I am not aware myself.'
John: 'Now I know them!'
Jacob: 'Now I know them, too!'

What are the two numbers?

John can eat 27 chocolates in an hour, Jacob can eat 2 chocolates in 10 minutes, and Jolly can eat 7 chocolates in 20 minutes. How long will it take them to share and eat a box of 120 chocolates whilst playing Chess?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

Your mother’s brother’s only brother-in-law is asleep on your couch. Who is asleep on your couch?

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

It belongs to you, but other people use it more than you do. What is it?