Question

递等式计算（能简便计算的要简便．）20.4×1.9-1.818.1×0.92+3.93（7.2-2）×1

递等式计算（能简便计算的要简便．）20.4×1.9-1.818.1×0.92+3.93（7.2-2）×1.21.25×0.7×0.81.2×2.5+0.8×2.54×7.8×2.5．

Answer 1

（1）20.4×1.9-1.8
=38.76-1.8
=36.96；

（2）18.1×0.92+3.93
=16.652+3.93
=20.582；

（3）（7.2-2）×1.2
=5.2×1.2
=6.24；

（4）1.25×0.7×0.8
=1.25×0.8×0.7
=1×0.7
=0.7；

（5）1.2×2.5+0.8×2.5
=（1.2+0.8）×2.5
=2×2.5
=5；

（6）4×7.8×2.5
=7.8×（4×2.5）
=7.8×10
=78．