题目内容
计算下面各题(能用简便方法的用简便方法).
22.7×1.25×O.8 | 3.91×2.8+6.09×2.8 |
9.83×(3.8-2.3)+1.5×6.17 | 3.6×51+36×4.9 |
7.8×9.9 | 5.4-3.2+12.6-7.8 |
7.2×4.1-9.5÷7.6 | 8.125×3+7×8.125 |
(0.75×27.5-3.405)÷0.8 | [0.16+(3-1.272)÷1.2]×1.25. |
解:(1)22.7×1.25×O.8,
=22.7×(1.25×O.8),
=22.7×1,
=22.7;
(2)3.91×2.8+6.09×2.8,
=(3.91+6.09)×2.8,
=10×2.8,
=28;
(3)9.83×(3.8-2.3)+1.5×6.17,
=9.83×1.5+1.5×6.17,
=(9.83+6.17)×1.5,
=16×1.5,
=24;
(4)3.6×51+36×4.9,
=3.6×51+(36÷10)×(4.9×10),
=3.6×51+3.6×49,
=(51+49)×3.6,
=100×3.6,
=360;
(5)7.8×9.9,
=7.8×(10-0.1),
=7.8×10-7.8×0.1,
=78-0.78,
=77.22;
(6)5.4-3.2+12.6-7.8,
=5.4+12.6-3.2-7.8,
=(5.4+12.6)-(3.2+7.8),
=18-11,
=7;
(7)7.2×4.1-9.5÷7.6,
=29.52-1.25,
=28.27;
(8)8.125×3+7×8.125,
=(3+7)×8.125,
=10×8.125,
=81.25;
(9)(0.75×27.5-3.405)÷0.8,
=(20.625-3.405)÷0.8,
=17.22÷0.8,
=21.525;
(10)[0.16+(3-1.272)÷1.2]×1.25.
=[0.16+1.728÷1.2]×1.25,
=[0.16+1.44]×1.25,
=1.6×1.25,
=2.
分析:(1)运用乘法结合律进行简算;
(2)运用乘法分配律进行简算;
(3)先算括号里的减法,然后乘法分配律进行简算;
(4)先把原式根据积不变规律变成:3.6×51+36×4.9=3.6×51+3.6×49,然后乘法分配律进行简算;
(5)原式7.8×9.9=7.8×(10-0.1),然后乘法分配律进行简算;
(6)原式5.4-3.2+12.6-7.8=5.4+12.6-3.2-7.8,然后运用减法的性质进行简算;
(7)、(9)、(10)按照运算顺序进行计算即可;
(8)运用乘法分配律进行简算.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.
=22.7×(1.25×O.8),
=22.7×1,
=22.7;
(2)3.91×2.8+6.09×2.8,
=(3.91+6.09)×2.8,
=10×2.8,
=28;
(3)9.83×(3.8-2.3)+1.5×6.17,
=9.83×1.5+1.5×6.17,
=(9.83+6.17)×1.5,
=16×1.5,
=24;
(4)3.6×51+36×4.9,
=3.6×51+(36÷10)×(4.9×10),
=3.6×51+3.6×49,
=(51+49)×3.6,
=100×3.6,
=360;
(5)7.8×9.9,
=7.8×(10-0.1),
=7.8×10-7.8×0.1,
=78-0.78,
=77.22;
(6)5.4-3.2+12.6-7.8,
=5.4+12.6-3.2-7.8,
=(5.4+12.6)-(3.2+7.8),
=18-11,
=7;
(7)7.2×4.1-9.5÷7.6,
=29.52-1.25,
=28.27;
(8)8.125×3+7×8.125,
=(3+7)×8.125,
=10×8.125,
=81.25;
(9)(0.75×27.5-3.405)÷0.8,
=(20.625-3.405)÷0.8,
=17.22÷0.8,
=21.525;
(10)[0.16+(3-1.272)÷1.2]×1.25.
=[0.16+1.728÷1.2]×1.25,
=[0.16+1.44]×1.25,
=1.6×1.25,
=2.
分析:(1)运用乘法结合律进行简算;
(2)运用乘法分配律进行简算;
(3)先算括号里的减法,然后乘法分配律进行简算;
(4)先把原式根据积不变规律变成:3.6×51+36×4.9=3.6×51+3.6×49,然后乘法分配律进行简算;
(5)原式7.8×9.9=7.8×(10-0.1),然后乘法分配律进行简算;
(6)原式5.4-3.2+12.6-7.8=5.4+12.6-3.2-7.8,然后运用减法的性质进行简算;
(7)、(9)、(10)按照运算顺序进行计算即可;
(8)运用乘法分配律进行简算.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.
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