题目内容
用递等式计算,能简算的要简算 (1)4×0.8×2.5×12.5 | (2) |
(3)6.78×8.5+1.5×6.78 | (4). |
解:(1)4×0.8×2.5×12.5,
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
(2)+2++3,
=(+)+(2+3),
=1+6,
=7;
(3)6.78×8.5+1.5×6.78,
=(8.5+1.5)×6.78,
=10×6.78,
=67.8;
(4)(++)×72,
=×72+×72+×72,
=30+8+27,
=65.
分析:(1)运用乘法交换律与结合律简算;
(2)运用加法交换律与结合律简算;
(3)、(4)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.
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
(2)+2++3,
=(+)+(2+3),
=1+6,
=7;
(3)6.78×8.5+1.5×6.78,
=(8.5+1.5)×6.78,
=10×6.78,
=67.8;
(4)(++)×72,
=×72+×72+×72,
=30+8+27,
=65.
分析:(1)运用乘法交换律与结合律简算;
(2)运用加法交换律与结合律简算;
(3)、(4)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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