计算下面各题(能简便的用简便方法计算).
10.15-10.75×0.4-5.7
5.8×(3.87-0.13)+4.2×3.74
32.52-(6+9.728)÷3.2×2.5
[(7.1-5.6)×0.9-1.15]÷2.5
5.4÷[2.6×(3.7-2.9)+0.62]
[20-(90.75÷6.6+2.25)]×11.6.
解:(1)10.15-10.75×0.4-5.7,
=10.15-4.3-5.7,
=10.15-(4.3+5.7),
=10.15-10,
=0.15;
(2)5.8×(3.87-0.13)+4.2×3.74,
=5.8×3.74+4.2×3.74,
=(5.8+4.2)×3.74,
=10×3.74,
=37.4;
(3)32.52-(6+9.728)÷3.2×2.5,
=32.52-15.728÷3.2×2.5,
=32.52-4.915×2.5,
=32.52-12.2875,
=20.2325;
(4)[(7.1-5.6)×0.9-1.15]÷2.5,
=[1.5×0.9-1.15]÷2.5,
=[1.35-1.15]÷2.5,
=0.2÷2.5,
=0.08;
(5)5.4÷[2.6×(3.7-2.9)+0.62],
=5.4÷[2.6×0.8+0.62],
=5.4÷[2.08+0.62],
=5.4÷2.7,
=2;
(6)[20-(90.75÷6.6+2.25)]×11.6,
=[20-(13.75+2.25)]×11.6,
=[20-16]×11.6,
=4×11.6,
=46.4.
分析:第(1)题,在进行10.15-4.3-5.7这一步计算时,应用减法的性质简算;
第(2)题在进行第二步计算时,应用乘法分配律的逆运算;
第(3)、(4)、(5)、(6)题不能简算,按顺序计算即可.
点评:此题考查了学生四则运算的顺序,以及灵活运用运算性质进行简算的能力.如上述第一题运用了减法的性质,即:
a-b-c=a-(b+c).