用递等式计算,能简算的要简算. (1)2-÷-(2)6÷[(+)×](3)(41×9.9+4.1)(4)(5)754-(302+459÷51)(6)9×(-)×13.
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解:
(1)2-÷-,
=2--,
=2-(+),
=2-2,
=0;
(2)6÷[(+)×],
=6÷[×],
=6÷,
=36;
(3)41×9.9+4.1,
=4.1×99+4.1,
=4.1×(99+1),
=4.1×100,
=410;
(4),
=×72+×72+×72,
=30+8+27,
=38+27,
=65;
(5)754-(302+459÷51),
=754-(302+9),
=754-311,
=443;
(6)9×(-)×13,
=9××13-9××13,
=26-9,
=17.
解析分析:(1)先算除法,再根据连减的性质进行计算;
(2)先算加法,再算乘法,最后算除法;
(3)根据乘法分配律进行计算;
(4)根据乘法分配律进行计算;
(5)先算除法,再算加法,最后算减法;
(6)根据乘法分配律进行计算.
点评:此题主要考查分数、小数和整数的四则混合运算的运算顺序和应用运算定律进行简便计算.