题目内容
用递等式计算.(能简算的要简算)
(1)0.78×0.45+0.55×0.78
(2)4.12×101-4.12
(3)(5.36+5.64)÷2.2
(4)0.265÷[(0.98+0.02)×0.5].
(1)0.78×0.45+0.55×0.78
(2)4.12×101-4.12
(3)(5.36+5.64)÷2.2
(4)0.265÷[(0.98+0.02)×0.5].
分析:(1)(2)运用乘法分配律简算;
(3)先算括号内的,再算括号外的;
(4)先算小括号内的,再算中括号内的,最后算括号外的.
(3)先算括号内的,再算括号外的;
(4)先算小括号内的,再算中括号内的,最后算括号外的.
解答:解:(1)0.78×0.45+0.55×0.78,
=0.78×(0.45+0.55),
=0.78×1,
=0.78;
(2)4.12×101-4.12,
=4.12×(101-1),
=4.12×100,
=412;
(3)(5.36+5.64)÷2.2,
=11÷2.2,
=5;
(4)0.265÷[(0.98+0.02)×0.5],
=0.265÷[1×0.5],
=0.265÷0.5,
=0.053.
=0.78×(0.45+0.55),
=0.78×1,
=0.78;
(2)4.12×101-4.12,
=4.12×(101-1),
=4.12×100,
=412;
(3)(5.36+5.64)÷2.2,
=11÷2.2,
=5;
(4)0.265÷[(0.98+0.02)×0.5],
=0.265÷[1×0.5],
=0.265÷0.5,
=0.053.
点评:此题考查了小数的四则混合运算,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.
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