11. (12 points) On the desktop, there are four square pieces of paper of different sizes with side lengths of $2, 3, 4, 5$. If one of the square pieces with side lengths of $2, 3, 4, 5$ is taken away respectively, then the area covered by the remaining three pieces of paper decreases by 2, 3, 4, 5, respectively. What is the total area covered by the four pieces of paper?
【Answer】Solution: As shown in the figure:
The areas of the four pieces of paper are $4$, $9$, $16$, and $25$,
The areas of the overlapping parts between each piece of paper are 2, 6, 12, and 20. Since $2+6+12=20$, the first three pieces of paper can only overlap with the fourth piece separately, with no part where three pieces overlap together. The overlapping area is 20, and the largest square piece of paper overlaps with the other three pieces, while the other three pieces do not overlap with each other. That is, there is only pairwise overlap, and the overlapping area is 20 square meters.

Therefore, the covered area is the total area of the four square pieces of paper minus 20 square meters, so the total covered area is:
$$
4+9+16+25-20=34
$$

Answer: The area covered by the four pieces of paper is 34.