2013年南京市白下区中考一模数学试题及答案(3)

2＝2±3．

x1＝2＋3，x2＝2－3． ·················································································· 6分

18．（本题6分）

解：解不等式①，得x＜2． ·························································································· 2分

解不等式②，得x≥－1． ······················································································· 4分 所以不等式组的解集是－1≤x＜2． ·········································································· 5分 所以不等式组的整数解是－1，0，1． ······································································· 6分

7

19．（本题6分）

a2－4a2＋2a2

解：(2－)÷ a－4a＋4a－2a－2

(a＋2)(a－2)a(a＋2)2＝[]÷ ··········································································· 3分 2－ (a－2)a－2a－2

a－2a

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

a－2a(a＋2)1

＝． ··········································································································· 6分

a＋2

20．（本题8分）

解：（1）因为24÷20%＝120(份)，所以本次抽取了120份电子小报． ··································· 2分 条形统计图中80分的份数是42，扇形统计图中80分的百分比是35%． ···················· 4分 （2）900×(30%＋10%) ··························································································· 6分

＝360(份)． ··································································································· 7分 所以估计该校学生比赛成绩达到90分以上（含90分）的电子小报有360份．

····································································································································· 8分

21．（本题8分）

解：（1）作图正确． ·································································································· 3分

（2）CF⊥AB．

理由如下：连接CD、CE、FD、FE． ··································· 4分 由作图知CD＝CE，FD＝FE． ············································ 5分 A

方法一：所以点C、F都在线段DE的垂直平分线上．

········································································ 7分

D ·P F

E B C 所以CF是线段DE的垂直平分线，即CF⊥AB． ······································ 8分

方法二：因为CF＝CF，所以△CDF≌△CEF． ···················································· 6分 所以∠DCF＝∠ECF． ········································································· 7分 又因为CD＝CE，所以CF⊥AB． ·························································· 8分

22．（本题8分）

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

3（2）分别转动两个转盘一次，所有可能出现的结果有：（1，4）、（1，5）、（1，

6）、（2，4）、（2，5）、（2，6）、（3，4）、（3，5）、（3，6），共有9种，它们出现的可能性相同．由于指针指向歌曲“3”时，该歌手就选择自己最擅长的歌曲“1”，所以所有的结果中，该歌手演唱歌曲“1”和“4”（记为

2

事件A）的结果有2种，所以P（A）＝． ······························································· 8分

9

8

（说明：通过枚举、画树状图或列表得出全部正确情况得4分；没有说明等可能性扣1分．）

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说中考初中2013年南京市白下区中考一模数学试题及答案(3)在线全文阅读。