What has many keys but can’t open a single lock?

Can you find out the total number of triangles in the given figure?

An American nightclub called 'The Coconut Grove' had a terrible fire in which over 400 people died. A simple design flaw in the building led to a high death toll. Subsequently, regulations were changed to ensure that all public buildings throughout the country eliminated this one detail, which proved deadly. What was it?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

You need to cut a round cake into eight equal pieces with just 3 cuts. Can you do it?

There was a greenhouse.
Inside the greenhouse, there is a white house.
Inside the white house, there is a red house.
Inside the red house, there are lots of babies.

What is It?

Can you find a five letter word that is left with only two letters if one is removed?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

What jumps when it walks and sits when it stands?

What makes this number unique: 8,549,176,320?