简便计算7.8乘3.04+5.96乘7.8+7.8 0.9999乘0.9+0.1111乘1.986.4除6.4-0.4 5.6乘1.25 13.7乘0.25-3.7除4

7.8×3.04+5.96×7.8+7.8 =7.8×（3.04+5.96+1）=7.8×10=780.9999×0.9+0.1111×1.9=0.1111×8.1+0.1111×1.9=0.1111×（8.1+1.9）=0.1111×10=1.11186.4÷6.4-0.4 =86.4÷1.6÷4-0.4=54÷4-0.4=13.5-0.4=13.15.6×...