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选择最适合的方法,写出递等式计算的过程
39.6-6.53+3.47. 0.0125×32×0.25. [90-(8.25÷0.6+1.25)]×0.01.
38×2.5+76+38×5.5. 3.6×31.4+43.9×6.4. 5.7×5.7+5.7×4.2+5.7×0.1.
分析:(1)从左往右依次计算;
(2)把32看作8×4,运用乘法结合律简算;
(3)先算小括号内的除法,再算小括号内的加法,然后算中括号内的减法,最后算括号外的乘法;
(4)把76看作38×2,运用乘法分配律简算;
(5)先算乘法,再算加法;
(6)运用乘法分配律简算.
解答:解:(1)39.6-6.53+3.47,
=33.07+3.47,
=36.54;

(2)0.0125×32×0.25,
=0.0125×8×4×0.25,
=(0.0125×8)×(4×0.25),
=0.1×1,
=0.1;

(3)[90-(8.25÷0.6+1.25)]×0.01,
=[90-(13.75+1.25)]×0.01,
=[90-15]×0.01,
=75×0.01,
=0.75;

(4)38×2.5+76+38×5.5,
=38×2.5+38×2+38×5.5,
=38×(2.5+2+5.5),
=38×10,
=380;

(5)3.6×31.4+43.9×6.4,
=113.04+280.96,
=394;

(6)5.7×5.7+5.7×4.2+5.7×0.1,
=5.7×(5.7+4.2+0.1),
=5.7×10,
=57.
点评:此题考查了小数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
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