What is so fragile that saying its name breaks it?

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.

Get total of 120 by using five zeros 0,0,0,0,0 and any one mathematical operator.
Do you ?

Replace the question mark with the correct number in the below-given picture?

Find the 8 in the below-given Image.

Can you place three balls such that the equation shown in the picture holds true?

What does this simple rebus mean?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

There are forty elephants and they have forty-fore heads. How can this be possible?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.