5. (10 points) In the figure, the side lengths of the squares are $2$, $4$, $6$, $8$, $10$ respectively, and the area of the shaded part is
40
【Solution】According to the analysis, subtract the area of the smallest square and the areas of other triangles from the area of the largest square,

The area of the other eight right-angled triangles $=2 \times \frac{1}{2} \times(2 \times 4+2 \times 6+2 \times 8+2 \times 10)=56$;
$$
S=10^{2}-2^{2}-2 \times \frac{1}{2}(2 \times 4+2 \times 6+2 \times 8+2 \times 10)=40 \text {. }
$$

Therefore, the answer is: 40 .