题目应该是：0.39×9.8+2×0.039这样的吧?0.39×9.8+2×0.039= 0.39×9.8+0.2×0.39=0.39×(9.8+0.2)=0.39×10=3.90.39×9.8＋2×3.9= 0.39×9.8+20×0.39=0.39×(9.8+20)=0.39×29.8（如果题目不变,后面凑不成10,无...