解:(1)18
-(10
+6.47),
=18
-10
-6.47,
=8-6.47,
=1.53;
(2)5
×45+45×3.6+45×120%,
=(5
+3.6+120%)×45,
=(5.2+3.6+1.2)×45,
=10×45,
=450;
(3)3
-(1
+
÷1
)×1
,
=3
-(1
+
×
)×1
,
=3
-(1
+
)×1
,
=3
-
×
,
=3
-
,
=
;
(4)3.8-2
÷[(3.2-1
)×
],
=3.8-2
÷[(3
-1
)×
],
=3.8-2
÷[
×
],
=3.8-2
÷
,
=3.8-
×
,
=3.8-2.1,
=1.7;
(5)19.99+1.999×990,
=1.999×10+1.999×990,
=1.999×(10+990),
=1.999×1000,
=1999;
(6)0.378×76000-378×66+84×378+37.8×60,
=378×76-378×66+84×378+378×6,
=378×(76-66+84+6),
=378×100,
=37800;
(7)(1
+2
+3
+1
)×(1-
),
=[(1
+3
)+(2
+1
)]×(1-
),
=[5+4]×
,
=9×
,
=
;
(8)0.24÷[(8.8-6
)÷1
]+
,
=
÷[(8
-6
)÷1
]+
,
=
÷[
×
]+
,
=
÷
+
,
=
×
+
,
=
+
,
=
.
分析:(1)运用后减法的性质简算;
(2)运用乘法分配律简算,同时注意数字转化;
(3)先算小括号内的除法,再算小括号内的加法,然后算括号外的乘法,最后算减法;
(4)先算小括号内的,再算中括号内的,然后算括号外的除法,最后算减法;
(5)根据数字特点,原式变为1.999×10+1.999×990,运用乘法分配律简算;
(6)根据数字特点,原式变为378×76-378×66+84×378+378×6,运用乘法分配律简算;
(7)第一个括号内运用加法交换律与结合律简算,同时计算第二个括号内的数据,最后算乘法;
(8)先算小括号内的,再算中括号内的,然后算括号外的除法,最后算加法.
点评:此题考查了小数、分数的四则混合运算,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.