题目内容
灵活计算,能用简便方法的要简算.
10.1×85 | 125×9.3×0.08 | 43.72×7.9+2.1×43.27 |
93÷0.25÷4 | 2.3+3.91÷(22-19.7) | 7.92×6-18.45÷3 |
6.78+6.78×99 | 18-(1.4+1.25×2.4) | 0.8×[13-(3.12+5.28)]. |
解:(1)10.1×85,
=(10+0.1)×85,
=850+8.5,
=858.5;
(2)125×9.3×0.08,
=125×0.08×9.3,
=10×9.3,
=93;
(3)43.72×7.9+2.1×43.27,
=43.72×(7.9+2.1),
=43.72×10,
=437.2;
(4)93÷0.25÷4,
=93÷(0.25×4),
=93÷1,
=93;
(5)2.3+3.91÷(22-19.7),
=2.3+3.91÷2.3,
=2.3+1.7,
=4;
(6)7.92×6-18.45÷3,
=47.52-6.15,
=41.37;
(7)6.78+6.78×99,
=6.78×(1+99),
=6.78×100,
=678;
(8)18-(1.4+1.25×2.4),
=18-(1.4+1.25×8×0.3),
=18-(1.4+3),
=18-4.4,
=13.6;
(9)0.8×[13-(3.12+5.28)],
=0.8×[13-8.4],
=0.8×4.6,
=3.68.
分析:(1)把10.1看作10+0.1,运用乘法分配律简算;
(2)运用乘法交换律与结合律简算;
(3)(7)运用乘法分配律简算;
(4)运用除法的性质简算;
(5)(9)先算括号内的,再算括号外的除法,最后算加法;
(6)先算乘除,再算减法;
(8)把2.4看作8×03,运用乘法分配律计算1.25×2.4,再算加法,组后算减法
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律简便计算.
=(10+0.1)×85,
=850+8.5,
=858.5;
(2)125×9.3×0.08,
=125×0.08×9.3,
=10×9.3,
=93;
(3)43.72×7.9+2.1×43.27,
=43.72×(7.9+2.1),
=43.72×10,
=437.2;
(4)93÷0.25÷4,
=93÷(0.25×4),
=93÷1,
=93;
(5)2.3+3.91÷(22-19.7),
=2.3+3.91÷2.3,
=2.3+1.7,
=4;
(6)7.92×6-18.45÷3,
=47.52-6.15,
=41.37;
(7)6.78+6.78×99,
=6.78×(1+99),
=6.78×100,
=678;
(8)18-(1.4+1.25×2.4),
=18-(1.4+1.25×8×0.3),
=18-(1.4+3),
=18-4.4,
=13.6;
(9)0.8×[13-(3.12+5.28)],
=0.8×[13-8.4],
=0.8×4.6,
=3.68.
分析:(1)把10.1看作10+0.1,运用乘法分配律简算;
(2)运用乘法交换律与结合律简算;
(3)(7)运用乘法分配律简算;
(4)运用除法的性质简算;
(5)(9)先算括号内的,再算括号外的除法,最后算加法;
(6)先算乘除,再算减法;
(8)把2.4看作8×03,运用乘法分配律计算1.25×2.4,再算加法,组后算减法
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律简便计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目