是乘以1.7吧?否则都除不尽了
法一：把7142.85分解质因数即得7142.85=3*3*3*5*11*13*37*0.01=5*11*13*27*37*0.01
7142.85÷3.7÷2.7×1.7×0.7
=5×11×13×27×37×0.01÷3.7÷2.7×1.7×0.7
=5×11×13×27×37÷37÷27×1.7×0.7
=5×11×13×1.7×0.7
=850.85
法二：
7142.85÷3.7÷2.7×1.7×0.7
=7142.85÷37÷27×17×7
=7142.85×7÷999×17
=49999.95÷999×17
=50.05×17
=850.85