解:(1)
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÷(
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+
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)×
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,
=
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×
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,
=
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,
=
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;
(2)3
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×7.4-3
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+3.6×3.125,
=3.125×(7.4+3.6-1),
=3.125×10,
=31.25;
(3)42
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÷7,
=(42
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)×
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,
=42×
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,
=6
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,
=6
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;
(4)52.75-
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-9.625,
=52.75-(0.375+9.625),
=52.75-10,
=42.75.
分析:(1)
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÷(
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+
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)×
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,根據(jù)分?jǐn)?shù)混合運(yùn)算的運(yùn)算順序,按照分?jǐn)?shù)四則運(yùn)算的計(jì)算法則進(jìn)行簡(jiǎn)算;
(2)3
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×7.4-3
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+3.6×3.125,把分?jǐn)?shù)化成小數(shù),再運(yùn)用乘法分配律進(jìn)行簡(jiǎn)算;
(3)42
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÷7,將原式轉(zhuǎn)化為:(42
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)×
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,再運(yùn)用乘法分配律進(jìn)行簡(jiǎn)算;
(4)52.75-
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-9.625,把
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化成小數(shù)0.375,再意義減法的運(yùn)算性質(zhì)進(jìn)行簡(jiǎn)算.
點(diǎn)評(píng):此題主要考查分?jǐn)?shù)四則混合運(yùn)算,要求學(xué)生牢固掌握運(yùn)算順序和計(jì)算法則,并且能夠靈活運(yùn)用運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算.