By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

You are an expert on paranormal activity and have been hired to locate a spirit haunting an old resort hotel. Strong signs indicate that the spirit lies behind one of four doors. The inscriptions on each door read as follows:

Door A: It's behind B or C
Door B: Its behind A or D
Door C: It's in here
Door D: It's not in here

Your psychic powers have told you three of the inscriptions are false, and one is true. Behind which door will you find the spirit?

If six children and two dogs were under an umbrella, how come none of them got wet?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

Replace the question mark with the correct number.

2 + 2= 4
3 + 3= 18
4 + 4= 48
5 + 5= ?

Take away the whole and some still remain. What is it?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

Which number should replace the question mark?

What can go through glass without breaking it?