12.小明统计了他家今年5月份打电话的次数及通话时间,并列出了频数分布表:
则通话时间不超过15分钟的频率是( )
| 通话时间x/分钟 | 0<x≤5 | 5<x≤10 | 10<x≤15 | 15<x≤20 |
| 频数(通话次数) | 20 | 16 | 9 | 5 |
| A. | 0.1 | B. | 0.4 | C. | 0.5 | D. | 0.9 |
11.不等式组$\left\{\begin{array}{l}{2x-1>0}\\{x+1≥0}\end{array}\right.$的解集是( )
| A. | x$>\frac{1}{2}$ | B. | -1$≤x<\frac{1}{2}$ | C. | x$<\frac{1}{2}$ | D. | x≥-1 |
10.不等式组$\left\{\begin{array}{l}{-2x+1<x+4}\\{\frac{x}{2}-\frac{x-1}{3}≤1}\end{array}\right.$的整数解( )个.
| A. | 3 | B. | 4 | C. | 5 | D. | 6 |
8.
如图,AC是⊙O的弦,OF⊥AC于点F,延长OF,与过点A的切线交于点P,若∠P=30°,AP=$\sqrt{3}$,则OF的值是( )
0 283959 283967 283973 283977 283983 283985 283989 283995 283997 284003 284009 284013 284015 284019 284025 284027 284033 284037 284039 284043 284045 284049 284051 284053 284054 284055 284057 284058 284059 284061 284063 284067 284069 284073 284075 284079 284085 284087 284093 284097 284099 284103 284109 284115 284117 284123 284127 284129 284135 284139 284145 284153 366461
| A. | $\frac{1}{2}$ | B. | 1 | C. | $\frac{\sqrt{3}}{2}$ | D. | $\sqrt{3}$ |