考点:整数、分数、小数、百分数四则混合运算,运算定律与简便运算
专题:运算顺序及法则
分析:(1)(4)(11)(12)根据四则混合运算中,有括号的先算括号里面的,再算括号外面的计算即可;
(2)(3)根据乘法的交换律与结合律解答即可;
(5)(6)(8)(10)根据乘法的分配律解答即可;
(7)根据减法的性质以及加法的结合律简算;
(9)根据除法的性质以及乘法的交换律与结合律简算.
解答:
解:(1)3-(12.9-84×
)
=3-(12.9-12)
=3-0.9
=2.1
(2)44.4×25
=11.1×(4×25)
=11.1×100
=1110
(3)
×(26×
)
=(
×
)×26
=
×26=6
(4)2-[
+(
-
)]
=2-[
+
]
=2-
=1
(5)7.25×1.8+27.5×0.18
=7.25×1.8+2.75×1.8
=(7.25+2.75)×1.8
=10×1.8
=18
(6)905×99+905
=905×(99+1)
=905×100
=90500
(7)[(
-
)+(
-
)]÷
=[(
+
)-(
+
)]÷
=[1-1]
÷=0
÷=0
(8)34×(
+
)×13
=34×13×
+
×13×34
=26+34
=60
(9)2000÷12.5÷25÷0.8÷4
=2000÷(12.5×25×0.8×4)
=2000÷[(12.5×0.8)×(25×4)]
=2000÷1000
=2
(10)
×
+
÷
=
×
+
×
=
×(
+
)
=
×1=
(11)[(
-
)×
]÷
=[
×
]÷
=
×=
(12)(
+
)÷(
÷4-
)
=
÷(
-
)
=
÷=
点评:考查了运算定律与简便运算,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定律简便计算.