What is common among 11, 69, and 88?

What does below chemistry rebus means?

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

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

Find the number of squares in the below-given picture.

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

Samuel was out for a walk when it started to rain. He did not have an umbrella and he wasn't wearing a hat. His clothes were soaked, yet not a single hair on his head got wet. How could this happen?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?