题目内容

脱式计算、能简算的要简算:
4
9
÷[
4
5
-( 
1
5
+
1
3
)]

8
15
×
5
6
×
4
9
5
6
÷
2
3
÷
5
6
5
6
×
7
8
+
5
6
×
1
8
(0.75-
3
16
 )×(
2
9
+
1
3
( 
7
9
+
5
27
)×54.
分析:(1)先算小括号里面的加法,再算中括号里面的减法,然后算括号外的除法;
(2)按照从左到右的顺序计算;
(3)先把除法变成乘法,运用乘法交换律简算;
(4)(6)运用乘法分配律简算;
(5)先同时运算小括号里面的减法和加法,再算括号外的乘法.
解答:解:(1)
4
9
÷[
4
5
-(
1
5
+
1
3
)],
=
4
9
÷[
4
5
-
1
5
-
1
3
],
=
4
9
÷[
3
5
-
1
3
],
=
4
9
÷
4
15

=
5
3


(2)
8
15
×
5
6
×
4
9

=
4
9
×
4
9

=
16
81


(3)
5
6
÷
2
3
÷
5
6

=
5
6
×
3
2
×
6
5

=
5
6
×
6
5
×
3
2

=1×
3
2

=
3
2


(4)
5
6
×
7
8
+
5
6
×
1
8

=
5
6
×(
7
8
+
1
8
),
=
5
6
×1,
=
5
6


(5)(0.75-
3
16
)×(
2
9
+
1
3
),
=
9
16
×
5
9

=
5
16


(6)(
7
9
+
5
27
)×54,
=
7
9
×54+
5
27
×54,
=42+10,
=52.
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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