问题 解答题
下面各题怎样算简便就怎样算.
7
9
-
7
9
÷7
2
3
×
8
5
+
1
3
÷
5
8
 
1
4
-
1
20
)×40
2-
3
8
÷
7
16
-
1
7
 
2
21
÷[(
3
4
-
2
3
)×
6
7
].
答案

(1)7÷

7
9
-
7
9
÷7,

=9-

1
9

=8

8
9

(2)

2
3
×
8
5
+
1
3
÷
5
8

=

2
3
×
8
5
+
1
3
×
8
5

=(

2
3
+
1
3
)×
8
5

=1×

8
5

=

8
5

(3)(

1
4
-
1
20
)×40,

=

1
4
×40-
1
20
×40,

=10-2,

=8;

(4)2-

3
8
÷
7
16
-
1
7

=2-

6
7
-
1
7

=2-(

6
7
+
1
7
),

=2-1,

=1;

(5)

2
21
÷[(
3
4
-
2
3
)×
6
7
],

=

2
21
÷[
1
12
×
6
7
],

=

2
21
÷
1
14

=

4
3

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