This applet provides an opportunity to pose questions that have more than one correct answer.[br][br]If one of the numbers - top, bottom or sum is hidden, then clearly there is one correct solution to the problem.[br][br]If two of these numbers are hidden - there are many solutions to the problem. How many?[br][br]If selected digits are masked then each problem has a finite number of correct solutions.[br][br]Can you find a solution?[br]How many solutions can you find?[br]How do you know you found them all?[br][br][b][i]Best viewed as a Java applet[/i][/b]