What does this below rebus puzzle mean?

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

Identify the 10 differences between the two given pictures.

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

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

Your job is to measure 45 minutes if you have only two cords and matches to light the cords.

1. The two cords are twisted from various materials, so their different segments can burn at different rates.
2. Each cord burns from end to end in exactly one hour.

Describe your way of measuring the 45 minutes.

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

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

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

I cannot talk, but I always reply when spoken to. What am I?

What is the fastest way to double your money?