神机妙算:(怎样简便就怎样算)
4+16÷÷×64-1×[-(-)]×0.53+75%×1.4725×3.2×1.25÷.
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解:(1)4+16÷,
=4+16×,
=4+20,
=24;
(2)÷×64-1,
=×64-1,
=-1,
=;
(3)×[-(-)],
=×[+-],
=×[1-],
=×,
=;
(4)×0.53+75%×1.47,
=0.75×0.53+0.75×1.47,
=(0.53+1.47)×0.75,
=2×0.75,
=1.5;
(5)25×3.2×1.25,
=25×0.4×8×1.25,
=10×(8×1.25),
=10×10,
=100;
(6)30÷,
=(30+)×,
=30×+×,
=28+,
=28.
解析分析:(1)把除法改为乘法,先算乘法,再算加法;(2)把除法改为乘法,从左向右依次计算;(3)运用减法的性质去掉小括号,运用加法交换律与结合律简算出中括号内的结果,再与括号外的相乘;(4)把分数和百分数化为小数,运用乘法分配律的逆运算简算;(5)根据数字特点,把3.2看作0.4×8,运用乘法结合律简算;(5)把30拆成(30+),同时把除法改为乘法,运用乘法结合律简算.
点评:此题重点考查学生从数字特点出发,运用性质、定律以及运算技巧,进行巧妙解答的能力.