9. (10 points) There are some identical square pieces of paper. Some of them are paired to form rectangles that are twice as long as they are wide. At this point, the total perimeter of all the newly formed rectangles is exactly equal to the total perimeter of the remaining squares, and it is known that the total perimeter of all the shapes after pairing is 40 centimeters less than the initial total perimeter. Therefore, the total perimeter of all the original square pieces of paper is ( ) centimeters.
A. 240
B. 260
C. 280
D. 300
【Solution】Solution:
According to the problem: When two squares are combined to form one rectangle, two sides of the squares are reduced,
then: From the perspective of sides, the perimeter of 1 rectangle $=6$ sides of squares, the perimeter of 2 rectangles $=12$ sides of squares $=3$ perimeters of squares,
that is: the perimeter of 2 rectangles $=3$ perimeters of squares;
From this perspective, we can group: Because 2 rectangles correspond to 3 squares, and at this point, the number of sides in each group is reduced by 4 sides compared to before the combination, a total reduction of 40 centimeters,
Therefore, it can be divided into $40 \div 4=10$ (groups), 10 groups have a total of squares $(2 \times 2+3) \times 10=70$ (squares), each side length $=4 \div 4=1$ (centimeter), the perimeter of 70 squares $=70 \times 4=280$ (centimeters).
Therefore, the answer is: $C$.