计算
19+2.4+2.91+14.6×153-0.6×53 80.7×8.7+8.07×13.21÷(+)÷ ÷[(-)÷].
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解:(1)19+2.4+2.91+14.6,
=(19+2.91)+(2.4+14.6),
=21.91+17,
=38.91;
(2)×153-0.6×53,
=0.6×153-0.6×53,
=(153-53)×0.6,
=100×0.6,
=60;
(3)80.7×8.7+8.07×13,
=8.07×87+8.07×13,
=(87+13)×8.07,
=100×8.07,
=807;
(4)(++)×30,
=×30+×30+×30,
=21+25+24,
=70;
(5)21÷(+)÷,
=21÷÷,
=21××,
=35;
(6)÷[(-)÷],
=÷[×],
=,
=×5,
=4.
解析分析:(1)运用加法结合律简算;(2)、(3)、(4)运用乘法分配律简算;(4)、(5)按照先算乘除,再算加减,有括号的先算括号里面的顺序计算.
点评:这类型的题目先观察算式,看能不能运用简便运算的方法简算,若不能就要按照运算法则运算.