1. 计算下列各题，能简算的要简算，写出主要计算过程。

28.9÷2.5÷0.4                                 72.6×27.4＋72.6×72.6     

5.98×11－5.98                       （0.58＋0.58＋0.58＋0.58）×2.5

4.6÷（1.6×12.5）                                                         2.33×3.4＋2.33×6.6

23.7÷2.5÷0.4                                                            （14.8－4.8÷2.5）×1.5

7.5÷(1.5+7.5×0.6)     1.9-1.9×0.9

3.6÷2.5÷0.4             0.18÷0.6+0.85

5.4×62+62×4.6       12.8÷[(19.8-16.6)÷1.6]