题目内容

写出计算的主要过程,能简便的要用简便方法计算.
12.75-
5
17
+1
1
4

6.3÷[(4
1
2
-0.07×50)×1
2
7
]
45×(
2
9
+
7
15
-
1
5

5
12
×0.8+
7
12
÷1.25.
(1)12.75-
5
17
+1
1
4

=12.75-
5
17
+1.25,
=12.75+1.25-
5
17

=14-
5
17

=13
12
17


(2)6.3÷[(4
1
2
-0.07×50)×1
2
7
],
=6.3÷[(4
1
2
-3.5)×1
2
7
],
=6.3÷[(4
1
2
-3
1
2
)×1
2
7
],
=6.3÷[(4
1
2
-3
1
2
)×1
2
7
],
=6.3÷[1×1
2
7
],
=6.3÷1
2
7

=6.3×
7
9

=4.9;

(3)45×(
2
9
+
7
15
-
1
5
),
=45×
2
9
+45×
7
15
-45×
1
5

=10+21-9,
=22;

(4)
5
12
×0.8+
7
12
÷1.25,
=
5
12
×0.8+
7
12
÷
5
4

=
5
12
×0.8+
7
12
×0.8,
=(
5
12
+
7
12
)×0.8,
=1×0.8,
=0.8.
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