Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

A man says, "Brothers and sisters, have I none, but that man's father is my father's son." Who is that man?

A prisoner is told: "If you tell a lie, we will hang you and if you tell the truth, we will shoot you." What did the prisoner say to save himself?

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.

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

I cannot talk, but I always reply when spoken to. What am I?

Why do you find that most of the buildings are deprived of the 13th floor?

The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member. Find how much younger is the new member ?