巧算.(1)12.5×3.9×8(2)4.3×2.5×0.4(3)0.125×6.4(4)36×0.25.

发布时间:2020-08-11 05:48:10

巧算.
(1)12.5×3.9×8
(2)4.3×2.5×0.4
(3)0.125×6.4
(4)36×0.25.

网友回答

解:(1)12.5×3.9×8,
=12.5×8×3.9,
=100×3.9,
=390;

(2)4.3×2.5×0.4,
=4.3×(2.5×0.4),
=4.3×1,
=4.3;

(3)0.125×6.4,
=0.125×8×0.8,
=1×0.8,
=0.8;

(4)36×0.25,
=9×4×0.25,
=9×(4×0.25),
=9×1,
=9.
解析分析:(1)运用乘法交换律与结合律简算;
(2)运用乘法结合律简算;
(3)把6.4看作8×0.8,运用乘法结合律简算;
(4)把36看作9×4,运用乘法结合律简算.

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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