When it's bad luck to meet a black cat?

Can you find out the number that should replace the question mark with a valid reason?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

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

How can you write nineteen in a manner that if we take out one, it becomes twenty?

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

Complete the table series riddle by finding the number that can replace "??".

Using eight eights and addition only, can you make 1000?

On my way to St. Ives I saw a man with 7 wives. Each wife had 7 sacks. Each sack had 7 cats. Each cat had 7 kittens. Kittens, cats, sacks, wives. How many were going to St. Ives?

If two fifty-foot ropes are suspended from a forty-foot ceiling that is twenty feet apart, how much rope will you be able to steal if you have a knife?