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

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

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

In the given picture, you can find two letters missing. When two particular letters are placed in the missing spots, you get an eight-letter word while reading in the anti-clockwise direction. Can you find out the missing letters and the missing word eventually?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and the cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

Which Travels Faster? Solve below famous picture riddle:

There is something which you can be arrested for attempting but not for successfully completing.

John said, "If yesterday was tomorrow, today would be Friday."

When did John make this statement?

The barber of Town shaves all men living in the town. No man living in the town is allowed to shave himself. The barber lives in that town. Who then shaves the barber of the town?