计算:7.77×31.08÷7.77101×0.5920×2.5×12.5×3.20.84÷14+0.84×(+)×24.
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解:①7.77×31.08÷7.77,
=7.77÷7.77×31.08,
=31.08;
②101×0.59,
=(100+1)×0.59,
=100×0.59+1×0.59,
=59+0.59,
=59.59;
③20×,
=(21-1)×,
=21×-,
=11-,
=10;
④2.5×12.5×3.2,
=2.5×12.5×8×0.4,
=(2.5×0.4)×(12.5×8),
=1×100,
=100;
⑤0.84÷14+0.84×,
=0.84×+0.84×,
=0.84×(+),
=084×1,
=0.84;
⑥(+)×24,
=×24+×24,
=20+9,
=29.
解析分析:①7.77×31.08÷7.77利用乘法的交换律计算;
②101×0.59把101变成100+1,再利用乘法的分配律计算;
③把20变成(21-1),再利用乘法的分配律计算;
④2.5×12.5×3.2把3.2变成8×0.4,再利用乘法的交换律和结合律变成(2.5×0.4)×(12.5×8)计算;
⑤0.84÷14+0.84×把0.84÷14变成0.84×,再利用乘法的分配律计算;
⑥利用乘法的分配律计算简便.
点评:考查了运算定律与简便运算,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.