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30°
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2010年大庆36中初四年级质量检测
数学试题答案
一、单项选择题(将正确答案的代号填在题后括号内,每小题3分,满分30分) 1. B 2.B 3. A 4. D 5B 6. C 7. D 8. B 9.B 10.B 二.填空题(每小题3分,满分24分) 11. 5
102.2? 12.x
y 3
-= 13. 28 14. 10 15 .5
2
-
16.23-≤<-a 1 7. 344或 18. 6cm 三、解答题(满分66分) 19. (满分5分)32+-
20. (满分6分)(1)该班60秒跳绳的平均次数至少是:
50
2
16051407120191001380460?+?+?+?+?+?=100.8.
因为100.8>100,所以一定超过全校平均次数. ············································ 3分
(2)这个学生的跳绳成绩在该班是中位数,由4+13+19=36,所以中位数一定在100~120范围内. ·················································································································· 5分
(3)该班60秒跳绳成绩大于或等于100次的有:19+7+5+2=33(人),
··············································· 6分
66050
33
.=. 所以,从该班任选一人,跳绳成绩达到或超过校平均次数的概率为0.66.
21. (满分6分)(1)过C 作CD AB ⊥,交AB 延长线于D 点,如图所示.………1分
则906030CAB ∠=-=,903060CBD ∠=-=,
30ACB CBD CAB ∴∠=∠-∠=, 30CAB ACB ∴∠=∠=,
500AB BC ∴==米,…………3分
在Rt CBD △中,
3
sin 605004252
CD BC ==?≈(米).
即所修公路长约为425米.…………4分
(2)依题意可得:200000
42550000350001000
?
-=(元) 3.5=(万元).
∴修建这条水泥公路村民需自筹资金3.5万元.…………6分 22. (满分9分)
(1)过A 作DC 的垂线AM 交DC 于M ,
则AM=BC=2,又tan ∠ADC=2,所以2
12
DM =
=.即DC=BC 。----3分 (2)等腰直角三角形。证△DEC ≌△BFC------3分 (3)设BE k =,则2CE CF k ==,所以22EF k =, 因为135BEC ∠=?,又45CEF ∠=?,所以90BEF ∠=?,
所以22(22)3BF k k k =+= ,
1sin 33k BFE k ∠=
=
。-------3分
23. (满分5分)(1)12
················································································ 1分 (2)
13
······································································································· 2分 (3)根据题意,画树状图: ············································································ 4分
(第23题图)
由树状图可知,共有16种等可能的结果:11,12,13,14,21,22,23,24,31,32,33,34,41,42,43,44.其中恰好是4的倍数的共有4种:12,24,32,44. 所以,P (4的倍数)41
164
=
=.---------------------5分 24.(满分8分)(1)330×13%=42.9(元)………………………………………………1分 42.9+120=162.9(元)
∴他共能获得162.9元的优惠.………………………………………………2分 (2)1200%13+=x y …………………………………………………………………4分
当王强购买的10部手机都选A 款时,此时x 最大 560×10×13%=728(元) 这时政府最多需付出补贴资金728元………………………………………6分
(3)横坐标依次是3300,5600;纵坐标依次是1629,1928.(答对一个给1分)-----8分 25. (满分8分)(1):∵AB 是直径
∴∠ACB =90o ,∴∠CAB +∠ABC =90o ··········································· 1分
∵∠MAC =∠ABC
∴∠MAC +∠CAB =90o,即MA ⊥AB
∴M N 是半圆的切线. ··························· 3分
(2)证法:
1 2 3 4 1 第一次 第二次 1 2 3 4 2 1 2 3 4 3 1 2 3 4 4 开始