2021年山东省临沂市郯城县中考一模数学试题

九年级数学试题答案 第 1 页 共 5 页 九年级数学试题参考答案及评分标准 说明：解答题给出了部分解答方法，考生若有其它解法，应参照本评分标准给分. 一、选择题（每小题 3分，共 42分） 题号 1 2 3 4 5 6 7 8 9 10 11 12 13 14 答案 A B D C A B C B D B D C A C 二、填空题（每小题 3分，共 15分） 15． 2)3(2  x ； 16．4； 17． 2 2 ； 18．5； 19．4. 三、解答题 20．解：原式= 22 4 xxx  ···································································· 2分 = 4x ·················································································· 4分 当 47  时················································································· 5分 原式= 447  ···········································································6分 = 7 ···················································································· 7分 21．解：（1）图形补充正确.·········································································2分 （2）方法一：由（1）知样本容量是 60， ∴该市 2014年（365天）空气质量达到“优”、“良”的总天数约为： 12 36 365 29260    （天）.··········································································· 5分 方法二：由（1）知样本容量是 60， ∴该市 2014年（365天）空气质量达到“优”的天数约为： 12 365 7360   （天）.·················································································· 3分 该市 2014年（365天）空气质量达到“良”的天数约为： 36 365 219 60   （天）.·················································································4分 某市若干天空气质量情况条形统计图 36 30 24 18 12 6 0 优 良 天数 空气质 量类别 重度 污染 轻微 污染 轻度 污染 中度 污染 12 36 3 2 1 6 九年级数学试题答案 第 2 页 共 5 页 ∴该市 2014年（365天）空气质量达到“优”、“良”的总天数约为： 73+219=292（天）.···················································································· 5分 （3）随机选取 2014年内某一天，空气质量是“优”的概率为： 12 1 . 60 5  ··································································································· 7分 22．解：过点 D作 DE⊥AC，垂足为 E，设 BE=x，········································· 2分 在 Rt△DEB中，tan∠DBE= BE DE ， ∵∠DBC=65°， ∴DE=xtan65°．·························································································4分 又∵∠DAC=45°， ∴AE=DE． ∴132+x=xtan65°， ∴解得 x≈115.8， ∴DE≈248（米）． ··················································································