Why Aeroplane windows are round?

Count the number of balls in picture below:

Using eight eights and addition only, can you make 1000?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

What is the end of everything?

Alpha is Beta's sister.

Gamma is a Beta mother.

Delta is Gamma's father.

Tango is Delta's mother.

Then,

How is Alpha related to Delta?

John was going on a jungle trip. He asked his wife to pack something to eat, something to drink and something to burn if he feels cold in the jungle. When John opens the backpack he found just one thing in the bag. What was it?