问题 解答题
用简便方法计算下面各题.
2
5
+
3
8
+
5
8
10-
1
5
-
4
5
5
18
-(
5
18
-
7
25
9
17
+(
5
12
+
8
17
4
9
+
1
16
+
15
16
+
5
9
16
25
-(
14
19
-
9
25
答案

(1)

2
5
+
3
8
+
5
8

=

2
5
+(
3
8
+
5
8
),

=

2
5
+1,

=1

2
5

(2)10-

1
5
-
4
5

=10-(

1
5
+
4
5
),

=10-1,

=9;

(3)

5
18
-(
5
18
-
7
25
),

=(

5
18
-
5
18
)+
7
25

=

7
25

(4)

9
17
+(
5
12
+
8
17
),

=(

9
17
+
8
17
)+
5
12

=1+

5
12

=1

5
12

(5)

4
9
+
1
16
+
15
16
+
5
9

=(

4
9
+
5
9
)+(
1
16
+
15
16
),

=1+1,

=2;

(6)

16
25
-(
14
19
-
9
25
),

=

16
25
-
14
19
+
9
25

=(

16
25
+
9
25
)-
14
19

=1-

14
19

=

5
19

单项选择题
单项选择题