Solution:

Four

As the window was closed it is obvious that the six candles that were not extinguished were lit till they melted away entirely. Thus only four candles that were extinguished remain at the end.

Solution:

What

Solution:

XIX is the answer which refers to nineteen in roman numeric system. On taking out one i.e. I, we will get XX that is equal to twenty.

Solution:

99 matches.

The number of matches will always sum up to one less than the number of players in a knock out tournament. You may calculate it in any manner. Thus 99 matches were played.

Solution:

I + IX = X

The equation read from the other side becomes X = XI + I which is false.

Solution:

Either your read from start or from ends, it will be same

Solution:

Chicago

Solution:

A green paint off-course :p

Solution:

I filled a glass full of water and held it over my head for 20 minutes.

Solution:

One Minute building

building 62 => Sixty second building => One minute building