用递等式计算,能简算的要简算.
78×10.1
(78.6-18.6÷0.31)×1.56.2×66.7+66.7×4.8-66.7(5.9+5.9+5.9+5.9)×0.25.
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解:(1)78×10.1,
=78×10+78×0.1,
=780+7.8,
=787.8;
(2)(78.6-18.6÷0.31)×1.5,
=(78.6-60)×1.5,
=18.6×1.5,
=27.9;
(3)6.2×66.7+66.7×4.8-66.7,
=(6.2+4.8-1)×66.7,
=10×66.7,
=667;
(4)(5.9+5.9+5.9+5.9)×0.25,
=9.5×(4×0.25),
=9.5×1,
=9.5.
解析分析:(1)78×10.1,运用乘法分配律进行简算;(2)(78.6-18.6÷0.31)×1.5,根据小数四则混合运算的顺序,按照小数四则运算的计算法则进行简算;(3)6.2×66.7+66.7×4.8-66.7,运用乘法分配律进行简算;(4)(5.9+5.9+5.9+5.9)×0.25,首先根据乘法的意义,将原式转化为:9.5×4×0.25,再运用乘法结合律进行简算.
点评:此题主要考查小数四则混合运算,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.