(1)495÷
+495÷45 (2)3.3×
+0.75×5
+75% (3)3.68-0.82-0.18
(4)56×
(5)1.25×32×0.25
(6)12×[
+(
)].解:(1)495÷
+495÷45,=495×
+495×
,=495×(
),=495×1,
=495;
(2)3.3×
+0.75×5
+75%,=3.3×0.75+0.75×5.7+0.75,
=0.75×(3.3+5.7+1),
=0.75×10,
=7.5;
(3)3.68-0.82-0.18,
=3.68-(0.82+0.18),
=3.68-1,
=2.68;
(4)56×
,=(57-1)×
,=57×
-
,=56-
,=55
;(5)1.25×32×0.25,
=1.25×8×4×0.25,
=(1.25×8)×(4×0.25),
=10×1,
=10;
(6)12×[
+(
)],=12×[
],=12×[1-
],=12×
,=10.
分析:(1)495÷
+495÷45,先把除法改为乘法,然后用乘法分配律的逆运算简算;(2)3.3×
+0.75×5
+75%,把
、5
和75%化为小数后,用乘法分配律的逆运算简算;(3)3.68-0.82-0.18,用减法的性质简算;
(4)56×
,把56看作(57-1),进行简算;(5)1.25×32×0.25,把32看成8×4,然后用乘法结合律简算;
(6)12×[
+(
)],先去小括号,
和
结合结果为1,中括号的结果的出后,与12约分.点评:此题重点考查学生的运算技巧,要想达到简算的目的,必须熟练掌握运算定律.