①2.07÷2.5÷0.4②21.36÷0.8-12.9
③0.125×32×2.5④0.65×201
⑤1.2×2.5+8×0.25⑥50.4×19+50.4.

解:①2.07÷2.5÷0.4,
=2.07÷(2.5×0.4),
=2.07÷1,
=2.07;

②21.36÷0.8-12.9,
=26.7-12.9,
=13.8;

③0.125×32×2.5,
=0.125×8×4×2.5,
=(0.125×8)×(4×2.5),
=1×10,
=10;

④0.65×201,
=0.65×(200+1),
=0.65×200+0.65×1,
=130+0.65,
=130.65;

⑤1.2×2.5+8×0.25,
=1.2×2.5+0.8×2.5,
=(1.2+0.8)×2.5,
=2×2.5,
=5;

⑥50.4×19+50.4,
=50.4×(19+1),
=50.4×20,
=1008.
分析:①根據(jù)連續(xù)除以?xún)蓚(gè)數(shù),等于除以這兩個(gè)數(shù)的積;
②先算除法,再算減法;
③把32分解成8×4,再運(yùn)用乘法結(jié)合律律簡(jiǎn)算;
④先把201分解成200+1,再運(yùn)用乘法分配律簡(jiǎn)算;
⑤先根據(jù)積不變規(guī)律,把8×0.25分解成0.8×2.5,再運(yùn)用乘法分配律簡(jiǎn)算;
⑥運(yùn)用乘法分配律簡(jiǎn)算.
點(diǎn)評(píng):此題是考查四則混合運(yùn)算,要仔細(xì)觀(guān)察算式的特點(diǎn),靈活運(yùn)用一些定律進(jìn)行簡(jiǎn)便計(jì)算.
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