问题 解答题
脱式计算.能简便计算的用简便方法计算.
①1
3
7
×
4
5
+2
4
7
×
4
5
+
4
5
②(
2
7
+
1
5
)×7×5
③12-
2
7
+
1
7
÷
1
5
8
9
×[
3
4
-(
7
16
-
1
4
)].
答案

①1

3
7
×
4
5
+2
4
7
×
4
5
+
4
5

=(1

3
7
+2
4
7
+1)×
4
5

=(4+1)×

4
5

=5×

4
5

=4;

②(

2
7
+
1
5
)×7×5,

=(

2
7
+
1
5
)×(7×5),

=

2
7
×(7×5)+
1
5
×(7×5),

=

2
7
×7×5+
1
5
×5×7,

=2×5+1×7,

=10+7,

=17;

③12-

2
7
+
1
7
÷
1
5

=12-

2
7
+
5
7

=12+(

5
7
-
2
7
),

=12+

3
7

=12

3
7

8
9
×[
3
4
-(
7
16
-
1
4
)],

=

8
9
×(
3
4
+
1
4
-
7
16
),

=

8
9
×(1-
7
16
),

=

8
9
×
9
16

=

1
2

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