5. Use square tiles of the same size to pave a square floor, with white tiles around the edges and black tiles in the middle (as shown in Fig. 1 and Fig. 2). When 80 white tiles are used around the square floor, the number of black tiles needed is $\qquad$.

保留源文本的换行和格式，直接输出翻译结果如下：

5. Use square tiles of the same size to pave a square floor, with white tiles around the edges and black tiles in the middle (as shown in Fig. 1 and Fig. 2). When 80 white tiles are used around the square floor, the number of black tiles needed is $\qquad$.
【Answer】 361 pieces
【Key Point】Square Array Problem
【Analysis】
On a square floor paved with 80 white tiles, the black tiles inside each row have $(80-4) \div 4=19$ pieces; therefore, the black tiles require $19 \times 19=361$ pieces.