题目内容
简算
2.04×92+20.4×0.8
100×
1.25×32×2.5
.
解:(1)2.04×92+20.4×0.8,
=20.4×9.2+20.4×0.8,
=20.4×(9.2+0.8),
=20.4×10,
=204;
(2)100×,
=(99+1)×,
=99×+1×,
=7+,
=7;
(3)1.25×32×2.5,
=1.25×8×4×2.5,
=(1.25×8)×(4×2.5),
=10×10,
=100;
(4)÷+÷,
=(+)÷,
=1÷,
=.
分析:(1)根据数字特点,先把原式变为20.4×9.2+20.4×0.8,运用乘法分配律简算;
(2)把100看作99+1,运用乘法分配律简算;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用除法的性质简算,然后根据倒数的概念,写出答案.或先把除法改为乘法,运用乘法分配律简算.
点评:完成此题,应注意审题,运用合适的简便方法计算.
=20.4×9.2+20.4×0.8,
=20.4×(9.2+0.8),
=20.4×10,
=204;
(2)100×,
=(99+1)×,
=99×+1×,
=7+,
=7;
(3)1.25×32×2.5,
=1.25×8×4×2.5,
=(1.25×8)×(4×2.5),
=10×10,
=100;
(4)÷+÷,
=(+)÷,
=1÷,
=.
分析:(1)根据数字特点,先把原式变为20.4×9.2+20.4×0.8,运用乘法分配律简算;
(2)把100看作99+1,运用乘法分配律简算;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用除法的性质简算,然后根据倒数的概念,写出答案.或先把除法改为乘法,运用乘法分配律简算.
点评:完成此题,应注意审题,运用合适的简便方法计算.
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