3. (8 points) As shown in the figure, with the four vertices $A, B, C, D$ of a regular octagon as centers, and the side length of the octagon as the radius, draw circles. The intersection points of the circular arcs are $E, F, G, H$. If the side length of the regular octagon is 100 cm, then the perimeter of the shaded area is $\qquad$ cm. ( $\pi$ is taken as 3.14)
【Solution】Solution: $180^{\circ} \times(8-2) \div 8$
$$
\begin{array}{l}
=180^{\circ} \times 6 \div 8 \\
=135^{\circ} \\
\frac{135}{180} \times 3.14 \times 100 \times \frac{1}{3} \times 4 \\
=\frac{1}{4} \times 3.14 \times 100 \times 4 \\
=314 \text { (cm) }
\end{array}
$$

Answer: The perimeter of the shaded part is 314 cm. Therefore, the answer is: 314.