解:(1)8×4×12.5×0.25,
=(8×12.5)×(4×0.25),
=100×1,
=100;
(2)8.7×2.9+71×0.87,
=8.7×2.9+7.1×8.7,
=8.7×(2.9+7.1),
=8.7×10,
=87;
(3)
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÷[(
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-
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)×24],
=
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÷[
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×24-
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×24],
=
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÷[20-16],
=
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÷4,
=
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;
(4)(
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+
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-
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)×12,
=
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×12+
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×12-
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×12,
=6+4-3,
=7.
分析:(1)8×4×12.5×0.25利用乘法的交換律和結(jié)合律變成(8×12.5)×(4×0.25)計(jì)算簡(jiǎn)便;
(2)8.7×2.9+71×0.87把71×0.87變成7.1×8.7,再利用乘法的分配律變成8.7×(2.9+7.1)計(jì)算簡(jiǎn)便;
(3)先算(
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-
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)×24利用乘法的分配律計(jì)算,再算括號(hào)外面的除;
(4)(
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+
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-
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)×12再利用乘法的分配律計(jì)算簡(jiǎn)便.
點(diǎn)評(píng):考查了運(yùn)算定律與簡(jiǎn)便運(yùn)算,四則混合運(yùn)算.注意運(yùn)算順序和運(yùn)算法則,靈活運(yùn)用所學(xué)的運(yùn)算律簡(jiǎn)便計(jì)算.