题目内容
选择合适的方法计算.
333×666+999×778 | ×7+0.25×5÷ |
8.69-1÷(0.375×+×0.8) | 538××3-2×0.538×125. |
解:(1)333×666+999×778,
=333×(3×222)+999×778,
=999×222+999×778,
=999×(222+778),
=999×1000,
=999000;
(2)×7+0.25×5÷,
=×7+×5×4,
=×(7+×4),
=×(7+22),
=×,
=;
(3)8.69-1÷(0.375×+×0.8),
=8.69-1÷(×+0.1),
=8.69-1÷(×+),
=8.69-1÷(+),
=8.69-÷,
=8.69-×,
=8.69-4,
=4.69;
(4)538××3-2×0.538×125,
=538××-2×538×0.125,
=538×(-×0.125),
=538×(1.35-0.35),
=538×1,
=538.
分析:(1)把666看作333×2,原式变为333×(3×222)+999×778,即999×222+999×778,运用乘法分配律简算.
(2)把除法改为乘法,运用乘法分配律简算.
(3)先算括号内的乘法,再算括号内的加法,然后算括号外的热除法,最后算减法.
(4)根据数字特点,原式变为538××-2×538×0.125,运用乘法分配律简算.
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.
=333×(3×222)+999×778,
=999×222+999×778,
=999×(222+778),
=999×1000,
=999000;
(2)×7+0.25×5÷,
=×7+×5×4,
=×(7+×4),
=×(7+22),
=×,
=;
(3)8.69-1÷(0.375×+×0.8),
=8.69-1÷(×+0.1),
=8.69-1÷(×+),
=8.69-1÷(+),
=8.69-÷,
=8.69-×,
=8.69-4,
=4.69;
(4)538××3-2×0.538×125,
=538××-2×538×0.125,
=538×(-×0.125),
=538×(1.35-0.35),
=538×1,
=538.
分析:(1)把666看作333×2,原式变为333×(3×222)+999×778,即999×222+999×778,运用乘法分配律简算.
(2)把除法改为乘法,运用乘法分配律简算.
(3)先算括号内的乘法,再算括号内的加法,然后算括号外的热除法,最后算减法.
(4)根据数字特点,原式变为538××-2×538×0.125,运用乘法分配律简算.
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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