2012年河北省初中毕业生升学文化课考试

数学试题参考答案

一、选择题（1~6小题，每小题2分；7~12小题，每小题3发，共30分）

题号123456789101112

答案BCACDBDABCAD

二、填空题（每小题3分，满分18分）

13.5　　14.52　　15.1　　16.　　17.21　　18.6

三、解答题（本大题共8小题，共72分）

19.解：

=······················································································· 5分

=4.············································································································ 8分

20.解：(1)设 km，则 km， km.

四边形是等腰梯形，，

外环公路总长和市区公路长的比为 .·················································· 3分

(2)由(1)可知，市区公路物长为 km，外环公路的总长为 km.

由题意，得 .························································································· 6分

解这个方程，得 .

.

答：市区公路的长为10km.···························································································· 8分

21.解：(1)4，6······································································································· 2分

(2)如图1··················································································································· 3分

(3)①乙····················································································································· 4分

=1.6.····································· 5分

由于，所以上述判断正确.················································································ 6分

②因为两人成绩的平均水平(平均数)相同，乙的成绩比甲稳定，所以乙将被选中.······ 8分

22.解：(1)由题意，，故点的坐标为(1，2).····························· 2分

反比例函数的图象经过点，

反比例函数的解析式为 ·················································································· 4分

(2)当时，

一次函数的图象一定过点.··············································· 6分

(3)设点的横坐标为 ··········································································· 8分

(注：对(3)中的取值范围，其他正确写法，均相应给分)

23.解：(1).······································································· 2分