There was an aeroplane crash, every single person died, but two people survived. How is this possible?

Can you replace the question mark with the correct number?

If two fifty-foot ropes are suspended from a forty-foot ceiling that is twenty feet apart, how much rope will you be able to steal if you have a knife?

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

What will you call your mother's brother's brother-in-law?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

What is the relationship between these matchstick pictures below?

Solve the mathematical equation in the picture below.

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?