1:1

Paper - solution


Let the sheet of paper have length x and width y. Then the uncovered area consists of two congruent rectangles of length x-y and width
y- 1
2
 x

. So the uncovered area is
2(x-y)(y- 1
2
 x)

, that is, (x-y)(2y-x).

The area covered twice is a rectangle of length y-(x-y), that is, 2y-x, and width
1
2
 x-(y- 1
2
 x)

, that is, (x-y). So the area covered twice is also (x-y)(2y-x).