问题 解答题
下面各题,怎样简便就怎样算.
(
3
8
+
4
5
)×40
3
4
+
5
8
×
2
5
4
9
×
4
15
+
4
15
×
5
9
(
2
7
+
4
21
7
16
9
11
×
11
5
×
7
3
(
8
9
-
5
12
2
17
答案

(1)(

3
8
+
4
5
)×40,

=

3
8
×40+
4
5
×40,

=15+32,

=47;

(2)

3
4
+
5
8
×
2
5

=

3
4
+
1
4

=1;

(3)

4
9
×
4
15
+
4
15
×
5
9

=

4
15
×(
4
9
+
5
9
),

=

4
15
×1,

=

4
15

(4)(

2
7
+
4
21
)×
7
16

=

10
21
×
7
16

=

5
24

(5)

9
11
×
11
5
×
7
3

=

9
5
×
7
3

=

21
5

(6)(

8
9
-
5
12
2
17

=

17
36
×
2
17

=

1
18

单项选择题
单项选择题