问题 解答题
灵活计算.
7
8
×
12
13
+
7
8
÷13
1
4
÷(3-
7
15
-
8
15
72×(
1
3
-
1
4
-
1
36
5
12
+
1
19
)×12+
7
19
3
4
-
3
4
×
2
5
)÷
1
5
1
21
×
1
17
×(2009×42×85)
答案

(1)

7
8
×
12
13
+
7
8
÷13,

=

7
8
×
12
13
+
7
8
×
1
13

=

7
8
×(
12
13
+
1
13
),

=

7
8
×1,

=

7
8

(2)

1
4
÷(3-
7
15
-
8
15
),

=

1
4
÷[3-(
7
15
+
8
15
)],

=

1
4
÷[3-1],

=

1
4
÷2,

=

1
8

(3)72×(

1
3
-
1
4
-
1
36
),

=72×

1
3
-72×
1
4
-72×
1
36

=24-18-2,

=4;

(4)(

5
12
+
1
19
)×12+
7
19

=

5
12
×12+
1
19
×12+
7
19

=5+(

12
19
+
7
19
),

=6;

(5)(

3
4
-
3
4
×
2
5
)÷
1
5

=[

3
4
×(1-
2
5
)]×5,

=[

3
4
×
3
5
]×5,

=

9
20
×5,

=

9
4

(6)

1
21
×
1
17
×(2009×42×85),

=(

1
21
×42)×(
1
17
×85)×2009,

=2×5×2009,

=20090;

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