Question 79
On a table there are $1999$ tea cups with their mouths facing upward initially. In each move, $100$ of them are turned upside down. After a number of moves, can they be turned so that all their mouths face downward? Why?
Answer the above two questions for the case where the number of cups is $1998$.
Answer the above two questions for the case where the number of cups is $1998$.