题目内容

(1)3
15
16
-2.1×
5
7
+1
7
8
÷30
(2)1999×199
4
5
-199.8×1998+
4
15

(3)3×
3
7
-
3
7
÷3+
3
7
÷3
(4)[1-(
3
4
-
7
12
)]÷(1
1
6
÷2
2
3
×
4
7

(5)(1
1
2
-0.375)÷[
1
25
×
(40%+2.1)].
(1)3
15
16
-2.1×
5
7
+1
7
8
÷30,
=3
15
16
-1.5+
15
8
×
1
30

=3
15
16
-1.5+
1
16

=3
15
16
+
1
16
-1.5,
=4-1.5,
=2.5;

(2)1999×199
4
5
-199.8×1998+
4
15

=1999×199
4
5
-199
4
5
×1998+
4
15

=(1999-1998)×199
4
5
+
4
15

=199
12
15
+
4
15

=200
1
15


(3)3×
3
7
-
3
7
÷3+
3
7
÷3,
=3×
3
7
-0,
=
9
7


(4)[1-(
3
4
-
7
12
)]÷(1
1
6
÷2
2
3
×
4
7
),
=[1-
1
6
]÷(
7
6
×
3
8
×
4
7
),
=
5
6
÷
1
4

=
5
6
×4,
=
10
3


(5)(1
1
2
-0.375)÷[
1
25
×
(40%+2.1)],
=(1.5-0.375)÷[0.04×(0.4+2.1)],
=1.125÷[0.04×2.5],
=1.125÷0.1,
=11.25.
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