递等式计算,能简算的就简算.
(1)18.23-8.39+11.77
(2)0.539+12.25-0.039
(3)5×1.2÷5×1.2
(4)8.5×10.1
(5)50.3×0.6-0.6
(6)0.25×23.9×0.4
(7)9.3+9.3×6.3+9.3×2.7
(8)0.53×(9.25-8.96)
解:(1)18.23-8.39+11.77,
=18.23+11.77-8.39,
=30-8.39,
=21.61;
(2)0.539+12.25-0.039,
=0.539-0.039+12.25,
=0.5+12.25,
=12.75;
(3)5×1.2÷5×1.2,
=6÷5×1.2,
=1.2×1.2,
=1.44;
(4)8.5×10.1,
=8.5×(10+0.1),
=8.5×10+8.5×0.1,
=85+0.85,
=85.85;
(5)50.3×0.6-0.6,
=(50.3-1)×0.6,
=49.3×0.6,
=29.58;
(6)0.25×23.9×0.4,
=0.25×0.4×23.9,
=0.1×23.9,
=2.39;
(7)9.3+9.3×6.3+9.3×2.7,
=9.3×(1+6.3+2.7),
=9.3×10,
=93;
(8)0.53×(9.25-8.96),
=0.53×0.29,
=0.1537.
分析:(1)根据加法的交换律和结合律,先算18.23+11.77再算减;
(2)根据加法的交换律和结合律,先算0.539-0.039再算加;
(3)从左到右依次计算;
(4)把10.1写成10+0.1,然后利用乘法的分配律;
(5)利用乘法分配律的逆运算,同时提取0.6,然后再计算;
(6)根据乘法的交换律和结合律,先算0.25×0.4;
(7)利用乘法分配律的逆运算,同时提取9.3,然后再计算;
(8)先算括号里面的再算乘.
点评:此题考查了小数加、减、乘、除的四则混合运算,能用简算的要简算.