解:(1)
×[
-(
-
)]
=
×[
+
-
],
=
×[1-
],
=
×
,
=
;
(2)[
-(
-
)]÷
=[
-
]×
,
=
×
,
=
;
(3)
÷
+
×
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(4)1.3-3.79+9.7-6.21
=(1.3+9.7)-(3.79+6.21),
=11-10,
=1;
(5)68×35-408÷24
=2380-17,
=2363;
(6)47.5-(0.6+6.4÷0.32)
=47.5-(0.6+20),
=47.5-20.6,
=26.9;
(7)1
+
÷4-
=1
+
-
,
=1
-
,
=
;
(8)
÷(
×
)-1
=
÷
-1
,
=1
-1
,
=
;
(9)
÷[
-(
+
)]
=
÷[
-
-
],
=
,
=
;
(10)(
-
)×15.
=
×15-
×15,
=9-5,
=4.
分析:(1)可根據(jù)一個數(shù)減兩個數(shù)的差,等于減去兩個數(shù)中的被減數(shù),加上減數(shù)的減法性質計算;
(2)(5)(6)(7)(8)根據(jù)四則混合運算的運算順序計算即可:先算乘除,再算加減,有括要先算括號里面的;
(3)(10)可根據(jù)乘法分配律計算;
(4)可根據(jù)加法交換律及一個數(shù)減兩個數(shù),等于減去這兩個數(shù)的減法性質計算.
(9)可根據(jù)一個數(shù)減去兩個數(shù)的和,等于分別減去這兩個數(shù)的減法性質計算.
點評:完成此類題目要注意分析式中數(shù)據(jù)的特點及內在聯(lián)系,然后運用合適的方法進行計算.