问题 解答题
用递等式计算
7
12
÷9+
1
9
×
5
12

[
4
5
-0÷(
1
3
+
2
5
)]×
5
8
(3.8-1.8÷2)×0.3
2
3
-
2
3
÷2
1
15
+
2
17
)×15×17
(15-15×
4
5
)×
7
24
答案

(1)

7
12
÷9+
1
9
×
5
12

=

7
12
×
1
9
+
1
9
×
5
12

=(

7
12
+
5
12
)×
1
9

=1×

1
9

=

1
9

(2)[

4
5
-0÷(
1
3
+
2
5
)]×
5
8

=

4
5
×
5
8

=

1
2

(3)(3.8-1.8÷2)×0.3,

=(3.8-0.9)×0.3,

=2.9×0.3,

=0.87;

(4)2÷

2
3
-
2
3
÷2,

=3-

1
3

=2

2
3

(5)(

1
15
+
2
17
)×15×17,

=

1
15
×15×17+
2
17
×15×17

=17+30,

=47;

(6)(15-15×

4
5
)×
7
24

=(15-12)×

7
24

=3×

7
24

=

7
8

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