题目内容

用简便方法计算
①5
3
7
-4
4
9
-6
5
9
+7
4
7

5
7
÷
5
2
+
30
7
×0.4
③(
5
9
+
4
5
-
7
15
)×45
④2012×
2011
2013
(1)5
3
7
-4
4
9
-6
5
9
+7
4
7

=5
3
7
+7
4
7
-(4
4
9
+6
5
9
),
=13-11,
=2;

(2)
5
7
÷
5
2
+
30
7
×0.4,
=(
5
7
+
30
7
)×
2
5

=5×
2
5

=2;

(3)(
5
9
+
4
5
-
7
15
)×45,
=
5
9
×
45+
4
5
×
45-
7
15
×
45,
=25+36-21,
=40;

(4)2012×
2011
2013

=(2013-1)×
2011
2013

=2013×
2011
2013
-1×
2011
2013

=2011-
2011
2013

=2000
2
2013
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