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

Solution:

Forty

Solution:

0! or cos(0)