下面各题,怎样简便就怎样算.
4×4.9×25???????????×+÷????????????7.6×99???????????????÷[×(+)]720÷15÷6???????????+÷??????????????++0.6+????????????(6+)÷3.
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解:(1)4×4.9×25,
=(4×25)×4.9,
=4.9×100,
=490;
(2),
=,
=(),
=×1,
=;
(3)7.6×99,
=7.6×(100-1),
=7.6×100-7.6,
=760-7.6,
=752.4;
(4)÷[×()],
=÷[×(+)];
=÷,
=×10,
=,
=1;
(5)720÷15÷6,
=720÷(15×6),
=720÷90,
=8;
(6)÷,
=+×6,
=4,
=4;
(7),
=()+(),
=1+1,
=2;
(8)(6+)÷3,
=(6+)×,
=6×+×,
=2+,
=2.
解析分析:(1)运用乘法的结合律及交换律进行计算.(2)(3)(8)运用乘法的分配律计算,使计算更加简便.(4)(6)根据四则混合运算的顺序进行计算,先算括号内部的再计算括号外面的,没有括号的先算乘除再算加减.(5)一个数连续除以两个数,可以用这个数除以这两个数的积.(7)把0.6化成分数,在运用加法的结合律及交换律进行计算.
点评:完成本题要注意分析式中数据,选择运用合适的简便方法计算.