能简便计算的要简便
①35.7-8.9-11.1+3.3????②4.6÷2.5÷0.4?????③2.7×9.9④2.56×1.7+1.44×1.7?????⑤(1-0.2)×[13-(3.12+5.28)].
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解:①35.7-8.9-11.1+3.3,
=35.7+3.3-(8.9+11.1),
=39-20,
=19;
②4.6÷2.5÷0.4,
=4.6÷(2.5×0.4),
=4.6÷1,
=4.6;
③2.7×9.9,
=2.7×(10-0.1),
=2.7×10-2.7×0.1,
=27-0.27,
=26.73;
④2.56×1.7+1.44×1.7,
=1.7×(2.56+1.44),
=1.7×4,
=6.8;
⑤(1-0.2)×[13-(3.12+5.28)],
=0.8×[13-8.4],
=0.8×4.6,
=3.68.
解析分析:①先把35.7和3.3相加,再根据连续减去两个数等于减去这两个数的和;
②根据连续除以两个数等于除以两个数的乘积;
③把9.9看作10-0.1,再利用乘法的分配律解答即可;
④运用乘法分配律进行简算;
⑤先算小括号里面的运算,再算中括号里面的.
点评:此题考查的目的是理解掌握乘法的运算定律,并且能够灵活运用乘法的运算定律对小数四则混合运算进行简便计算.