脱式计算.(能用简便方法的用简便方法).
3.78-1.46+1.54
17.5-5.15-1.854.1×9.90.4×(2.5+0.25)
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解:(1)3.78-1.46+1.54,
=2.32+1.54,
=3.86;
(2)17.5-5.15-1.85,
=17.5-(5.15+1.85),
=17.5-7,
=10.5;
(3)4.1×9.9,
=4.1×(10-0.1),
=41-0.41,
=40.59;
(4)0.4×(2.5+0.25),
=0.4×2.5+0.4×0.25,
=1+0.1,
=1.1.
解析分析:(1)从左往右依次计算;(2)运用减法的性质简算;(3)把9.9看作(10-0.1),运用乘法分配律简算;(4)运用乘法分配律简算.
点评:此题考查了小数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.