题目内容
(1)3
-2.1×
+1
÷30
(2)1999×199
-199.8×1998+
(3)3×
-
÷3+
÷3
(4)[1-(
-
)]÷(1
÷2
×
)
(5)(1
-0.375)÷[
×(40%+2.1)].
| 15 |
| 16 |
| 5 |
| 7 |
| 7 |
| 8 |
(2)1999×199
| 4 |
| 5 |
| 4 |
| 15 |
(3)3×
| 3 |
| 7 |
| 3 |
| 7 |
| 3 |
| 7 |
(4)[1-(
| 3 |
| 4 |
| 7 |
| 12 |
| 1 |
| 6 |
| 2 |
| 3 |
| 4 |
| 7 |
(5)(1
| 1 |
| 2 |
| 1 |
| 25 |
(1)3
-2.1×
+1
÷30,
=3
-1.5+
×
,
=3
-1.5+
,
=3
+
-1.5,
=4-1.5,
=2.5;
(2)1999×199
-199.8×1998+
,
=1999×199
-199
×1998+
,
=(1999-1998)×199
+
,
=199
+
,
=200
;
(3)3×
-
÷3+
÷3,
=3×
-0,
=
;
(4)[1-(
-
)]÷(1
÷2
×
),
=[1-
]÷(
×
×
),
=
÷
,
=
×4,
=
;
(5)(1
-0.375)÷[
×(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.
| 15 |
| 16 |
| 5 |
| 7 |
| 7 |
| 8 |
=3
| 15 |
| 16 |
| 15 |
| 8 |
| 1 |
| 30 |
=3
| 15 |
| 16 |
| 1 |
| 16 |
=3
| 15 |
| 16 |
| 1 |
| 16 |
=4-1.5,
=2.5;
(2)1999×199
| 4 |
| 5 |
| 4 |
| 15 |
=1999×199
| 4 |
| 5 |
| 4 |
| 5 |
| 4 |
| 15 |
=(1999-1998)×199
| 4 |
| 5 |
| 4 |
| 15 |
=199
| 12 |
| 15 |
| 4 |
| 15 |
=200
| 1 |
| 15 |
(3)3×
| 3 |
| 7 |
| 3 |
| 7 |
| 3 |
| 7 |
=3×
| 3 |
| 7 |
=
| 9 |
| 7 |
(4)[1-(
| 3 |
| 4 |
| 7 |
| 12 |
| 1 |
| 6 |
| 2 |
| 3 |
| 4 |
| 7 |
=[1-
| 1 |
| 6 |
| 7 |
| 6 |
| 3 |
| 8 |
| 4 |
| 7 |
=
| 5 |
| 6 |
| 1 |
| 4 |
=
| 5 |
| 6 |
=
| 10 |
| 3 |
(5)(1
| 1 |
| 2 |
| 1 |
| 25 |
=(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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