How can you make number one disappear by adding something to it?

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

Do You See It?

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

I can write cow in 13 letters.

Can You?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

Complete the following series. It.s very logical:

1, 4, 5, 6, 7, 9, 11, __?

The chance of Mr John winning the lottery is 10%. All participants lined up and Mr John is 4th in the row. The first three participants lose the lottery.

What is the chance of Mr John now?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?