Why Aeroplane windows are round?

There were three women in all the swimming costumes!
One was happy and the other two were sad!
The happy one was crying and the sad ones were smiling.
Why was this?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

French Police inspects a room where there are no windows, no doors, no tables and is almost empty expect there is just a puddle of water. They found a dead man who obviously hung herself from the ceiling, but they are not able to figure out how this had happened.

John and Jacob entered the crime scene and easily able to solve the case.

How did the man die?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

Look at the picture and find out which square is not linked with any of the other squares.

Solve below popular number sequence
314 159 265 358 979 323 846 ?

If one and a half boys, eat one and a half burgers in one and a half hours.

How many burgers can 9 boys eat in 3 hours?

how come the second man dies?