问题 解答题
用简便方法计算
23
21
-
7
13
-
6
13

(
55
18
-
11
36
1
72
答案

(1)

23
21
-
7
13
-
6
13

=

23
21
-(
7
13
+
6
13
),

=

23
21
-1,

=

2
21

(2)(

55
18
-
11
36
1
72

=(

55
18
-
11
36
)×72,

=

55
18
×72-
11
36
×72,

=220-22,

=198.

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单项选择题 B1型题