安阳市2013—2014学年下期末考试八年级数学答案.pdf

2013—2014 学年第二学期教学质量抽测 八年级数学参考答案及评分意见 一、选择题 （每题2 分，共14 分） 题号 1 2 3 4 5 6 7 答案 C C D B A D B 二、填空题 （每题3 分，共24 分） 8. m 0 9. ＜ 10. 4 11.等腰直角三角形 x 4,  12. y x 10 13.  14. 4.8 15. 2 3或2 5 y 2  三、解答题 （本大题有7 个题目，共62 分） 16. 解：原式 3 33 3 2  3 ······················································4 分 = 3 3 1 . ······································································6 分 17. 解：（1）这15 名学生家庭年收入的平均数是： （2×1+2.5×3+3×5+4×2+5×2+9×1+13×1 ）÷15=4.3 （万元）.·························3 分 将这 15 个数据从小到大排列，最中间的数（第8 个）是3，故这组数据的中位数 是3. ··································································································5 分 在这一组数据中3 出现次数最多，所以这组数据的众数是3. ··················6 分 （2 ）用众数或中位数代表这15 名学生家庭年收入的一般水平较为合适. 因为本题中个 别极端值抬高了平均数的值，而3 在这组数据中出现的次数最多，也是这组数据的中 位数，所以用众数或中位数代表家庭年收入的一般水平 （3 万元）较为合适. ····8 分 18. 解：∵在Rt△ABC 中，∠C=90°，∠A=30°， ∴ABC 60. ·················································································1 分 ∵ 是ABC 的平分线, BD ∴ABD CBD 30 , ···································································2 分 八年级数学参考答案 第1 页 共4 页  又∵Rt△ CBD 中，CBD 30 CD 5 cm. ∴BD 2CD 10cm. ··········································································4 分 根据勾股定理得BC 5 3 cm.································································6 分 在Rt△ ABC 中，∠A=30°， AB 2BC 10 3 cm. ·········································································8 分