Why Aeroplane windows are round?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

Manish and Manoj play 5 games of chess.
Both Manish and Manoj win the exact same number of games. There is no tie at all.

How?

How can you throw a ball as hard as you can and have it come back to you even if it doesn't hit anything there is nothing attached to it and no one else catches or throws it.

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

A container contains 100 eggs. They can be either fresh or rotten. What is sure is the fact that there is at least one fresh egg in that container.

If you are asked to pick two eggs randomly from the container, at least one of them will be rotten.

Can you calculate how many eggs in that container are fresh?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

If your uncle’s sister is not your aunt, what relation is she to you?

How many triangles do you see in the picture puzzle below?