1. 计算下列各题，要写出主要计算过程，怎样简便就怎样计算。

①1.25×12×8           ②4×18.7+6.3×4

③9.8÷2.5÷4            

（1）0.25×9.3×4                                 （2）0.83×53＋8.3×4.7

（3）5.4÷1.25÷8                                 （4）（2.1＋6.9÷0.15）÷0.2

(12.5-0.25) ×0.4    12.5÷0.5÷0.4    8÷(1.76-1.36)×1.8

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