What number should come in place of the question mark below?

A girl was sitting in her hotel room when she heard a knock on the door. She opened the door and found that a man was standing outside. The man said, "Oh! I am really sorry, I thought this was my room." He then walked through the corridor to the elevator. The girl did not know the man. She closed her door and called security asking them to apprehend the man. What made her suspicious of that man? He might have been genuinely mistaken.

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

When we see 2 but call 10?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that 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?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Can you identify if it's a murder or a suicide ?